PostIt: validate/refuse an estimate with a signature (pro or client)

Adds the client-side ability to open an estimate from the list, draw a
signature on a reusable SignaturePadView control, and accept or reject it
against /api/v1/front/query/accept|reject. The server resolves the actor
role (provider vs client) from the caller's identity, so the same page works
for either party.

- Yavsc.Api.Client: QueryAcceptanceDto + FrontOfficeApiClient (accept/reject)
- PostIt: extract SignaturePadView UserControl from SignaturePage; new
  EstimateValidationPage (VM + view) with Valider/Refuser/Effacer/Retour;
  wire OpenEstimate entry point from EstimateListPage; register client/page
  in DI + ViewLocator
- Tests: FrontOfficeApiClient + EstimateValidationPageViewModel unit tests;
  update EstimateListPageViewModelTests ctor

Co-Authored-By: Claude Code <noreply@anthropic.com>

src/PostIt/PostIt.Tests/EstimateListPageViewModelTests.cs

@@ -11,7 +11,8 @@ public class EstimateListPageViewModelTests
     {
         var api = new StubEstimateListApi();
         var client = new EstimateApiClient(api, "https://business.example/api/v1/");
-        var vm = new EstimateListPageViewModel(client, EstimateListPerspective.Client);
+        var front = new FrontOfficeApiClient(api, "https://business.example/api/v1/");
+        var vm = new EstimateListPageViewModel(client, EstimateListPerspective.Client, front);
 
         await vm.InitializeAsync();
 
@@ -28,7 +29,8 @@ public class EstimateListPageViewModelTests
     {
         var api = new StubEstimateListApi();
         var client = new EstimateApiClient(api, "https://business.example/api/v1/");
-        var vm = new EstimateListPageViewModel(client, EstimateListPerspective.Provider);
+        var front = new FrontOfficeApiClient(api, "https://business.example/api/v1/");
+        var vm = new EstimateListPageViewModel(client, EstimateListPerspective.Provider, front);
 
         await vm.InitializeAsync();
 
@@ -42,7 +44,8 @@ public class EstimateListPageViewModelTests
     {
         var api = new StubEstimateListApi();
         var client = new EstimateApiClient(api, "https://business.example/api/v1/");
-        var vm = new EstimateListPageViewModel(client, EstimateListPerspective.Provider);
+        var front = new FrontOfficeApiClient(api, "https://business.example/api/v1/");
+        var vm = new EstimateListPageViewModel(client, EstimateListPerspective.Provider, front);
 
         await vm.InitializeAsync();
 
@@ -63,7 +66,8 @@ public class EstimateListPageViewModelTests
     {
         var api = new StubEstimateListApi { Empty = true };
         var client = new EstimateApiClient(api, "https://business.example/api/v1/");
-        var vm = new EstimateListPageViewModel(client, EstimateListPerspective.Client);
+        var front = new FrontOfficeApiClient(api, "https://business.example/api/v1/");
+        var vm = new EstimateListPageViewModel(client, EstimateListPerspective.Client, front);
 
         await vm.InitializeAsync();
 

src/PostIt/PostIt.Tests/EstimateValidationPageViewModelTests.cs

@@ -0,0 +1,166 @@
+using System;
+using System.Net.Http;
+using PostIt.Controls;
+using PostIt.ViewModels;
+using Yavsc.Api.Client;
+
+namespace PostIt.Tests;
+
+/// <summary>
+/// Verifies <see cref="EstimateValidationPageViewModel"/> wires the
+/// signature pad + perspective into the right
+/// <see cref="FrontOfficeApiClient"/> call. The view (XAML, rendering)
+/// is not tested here; the VM is driven through the same
+/// <see cref="SignaturePadControl"/> test hooks the signature tests use,
+/// and the API client through a recording fake
+/// <see cref="IYavscApiClient"/>. The test host's
+/// <c>TestApp</c> makes <c>GoBackAsync</c> a no-op, so the success paths
+/// run to completion without navigation side effects.
+/// </summary>
+public class EstimateValidationPageViewModelTests
+{
+    private static EstimateDto SampleEstimate(long? commandId = 42) => new()
+    {
+        Id = 7,
+        CommandId = commandId,
+        CommandType = "Rdv",
+        Title = "Devis plomberie",
+        Description = "Réparation",
+        ClientId = "bob",
+        OwnerId = "alice",
+    };
+
+    private static void DrawOneStroke(SignaturePadControl pad)
+    {
+        pad.AppendPointForTest(100, 200);
+        pad.AppendPointForTest(300, 400);
+        pad.SealStrokeForTest();
+    }
+
+    [Fact]
+    public async Task Validate_calls_accept_with_strokes_and_command_id()
+    {
+        var api = new RecordingApi();
+        var front = new FrontOfficeApiClient(api, "https://business.example/api/v1/");
+        var vm = new EstimateValidationPageViewModel(
+            SampleEstimate(), EstimateListPerspective.Provider, front);
+
+        var pad = new SignaturePadControl();
+        vm.Attach(pad);
+        DrawOneStroke(pad);
+
+        await vm.ValidateAsync();
+
+        Assert.Equal(HttpMethod.Post, api.LastMethod);
+        Assert.Contains("front/query/accept", api.LastPath);
+        Assert.Contains("billingCode=Rdv", api.LastPath);
+        Assert.Contains("queryId=42", api.LastPath);
+        var body = Assert.IsType<QueryAcceptanceRequestDto>(api.LastBody);
+        Assert.NotNull(body.Strokes);
+        Assert.NotEmpty(body.Strokes);
+        Assert.Equal(10_000, body.CoordinateMax);
+    }
+
+    [Fact]
+    public async Task Reject_calls_reject_endpoint_with_no_body()
+    {
+        var api = new RecordingApi();
+        var front = new FrontOfficeApiClient(api, "https://business.example/api/v1/");
+        var vm = new EstimateValidationPageViewModel(
+            SampleEstimate(), EstimateListPerspective.Client, front);
+
+        vm.Attach(new SignaturePadControl());
+
+        await vm.RejectAsync();
+
+        Assert.Equal(HttpMethod.Post, api.LastMethod);
+        Assert.Contains("front/query/reject", api.LastPath);
+        Assert.Contains("queryId=42", api.LastPath);
+        Assert.Null(api.LastBody);
+    }
+
+    [Fact]
+    public async Task Validate_without_signature_warns_and_does_not_call()
+    {
+        var api = new RecordingApi();
+        var front = new FrontOfficeApiClient(api, "https://business.example/api/v1/");
+        var vm = new EstimateValidationPageViewModel(
+            SampleEstimate(), EstimateListPerspective.Provider, front);
+
+        vm.Attach(new SignaturePadControl()); // empty pad
+
+        await vm.ValidateAsync(); // no throw: returns before GoBack
+
+        Assert.Null(api.LastMethod);
+        Assert.Contains("signer", vm.StatusMessage, StringComparison.OrdinalIgnoreCase);
+    }
+
+    [Fact]
+    public void Validate_command_gates_on_signature_and_command()
+    {
+        var api = new RecordingApi();
+        var front = new FrontOfficeApiClient(api, "https://business.example/api/v1/");
+        var vm = new EstimateValidationPageViewModel(
+            SampleEstimate(commandId: null), EstimateListPerspective.Provider, front);
+
+        var pad = new SignaturePadControl();
+        vm.Attach(pad);
+
+        // No CommandId ⇒ cannot validate even after signing.
+        DrawOneStroke(pad);
+        Assert.False(vm.ValidateCommand.CanExecute(null));
+
+        var vm2 = new EstimateValidationPageViewModel(
+            SampleEstimate(), EstimateListPerspective.Provider, front);
+        var pad2 = new SignaturePadControl();
+        vm2.Attach(pad2);
+        Assert.False(vm2.ValidateCommand.CanExecute(null)); // no signature yet
+        DrawOneStroke(pad2);
+        Assert.True(vm2.ValidateCommand.CanExecute(null));
+    }
+
+    [Fact]
+    public void RoleLabel_reflects_perspective()
+    {
+        var front = new FrontOfficeApiClient(new RecordingApi(), "https://business.example/api/v1/");
+        var pro = new EstimateValidationPageViewModel(
+            SampleEstimate(), EstimateListPerspective.Provider, front);
+        var cli = new EstimateValidationPageViewModel(
+            SampleEstimate(), EstimateListPerspective.Client, front);
+
+        Assert.Contains("prestataire", pro.RoleLabel, StringComparison.OrdinalIgnoreCase);
+        Assert.Contains("client", cli.RoleLabel, StringComparison.OrdinalIgnoreCase);
+    }
+
+    private sealed class RecordingApi : IYavscApiClient
+    {
+        public HttpClient Http { get; } = new();
+        public HttpMethod? LastMethod { get; private set; }
+        public string? LastPath { get; private set; }
+        public object? LastBody { get; private set; }
+
+        public Task<T> CallAsync<T>(HttpMethod method, string path, object? body = null, CancellationToken ct = default)
+        {
+            LastMethod = method;
+            LastPath = path;
+            LastBody = body;
+            return Task.FromResult(default(T)!);
+        }
+
+        public Task CallAsync(HttpMethod method, string path, object? body = null, CancellationToken ct = default)
+        {
+            LastMethod = method;
+            LastPath = path;
+            LastBody = body;
+            return Task.CompletedTask;
+        }
+
+        public Task<T> CallAsync<T>(HttpMethod method, string path, Func<HttpContent> contentFactory, CancellationToken ct = default)
+            => CallAsync<T>(method, path, (object?)null, ct);
+
+        public Task CallAsync(HttpMethod method, string path, Func<HttpContent> contentFactory, CancellationToken ct = default)
+            => CallAsync(method, path, (object?)null, ct);
+
+        public ValueTask DisposeAsync() => ValueTask.CompletedTask;
+    }
+}

src/PostIt/PostIt.Tests/FrontOfficeApiClientTests.cs

@@ -0,0 +1,121 @@
+using System.Net.Http;
+using Yavsc.Api.Client;
+
+namespace PostIt.Tests;
+
+/// <summary>
+/// Verifies <see cref="FrontOfficeApiClient"/> issues the right
+/// <c>api/v1/front/query/accept</c> / <c>.../reject</c> requests with
+/// the PostIt signature payload, using a recording fake
+/// <see cref="IYavscApiClient"/> (no network).
+/// </summary>
+public class FrontOfficeApiClientTests
+{
+    private static QueryAcceptanceRequestDto SampleBody() => new()
+    {
+        Strokes = new[] { 2, 100, 200, 300, 400 },
+        CoordinateMax = 10_000,
+        CapturedAtUtc = new DateTime(2026, 9, 21, 12, 0, 0, DateTimeKind.Utc),
+    };
+
+    [Fact]
+    public async Task Accept_posts_to_accept_endpoint_with_signature_body()
+    {
+        var api = new RecordingApi();
+        var client = new FrontOfficeApiClient(api, "https://business.example/api/v1/");
+
+        var body = SampleBody();
+        await client.AcceptQueryAsync("Rdv", 42, body);
+
+        Assert.Equal(HttpMethod.Post, api.LastMethod);
+        Assert.Equal(
+            "https://business.example/api/v1/front/query/accept?billingCode=Rdv&queryId=42",
+            api.LastPath);
+        Assert.Same(body, api.LastBody);
+    }
+
+    [Fact]
+    public async Task Reject_posts_to_reject_endpoint_with_no_body()
+    {
+        var api = new RecordingApi();
+        var client = new FrontOfficeApiClient(api, "https://business.example/api/v1/");
+
+        await client.RejectQueryAsync("Rdv", 42);
+
+        Assert.Equal(HttpMethod.Post, api.LastMethod);
+        Assert.Equal(
+            "https://business.example/api/v1/front/query/reject?billingCode=Rdv&queryId=42",
+            api.LastPath);
+        Assert.Null(api.LastBody);
+    }
+
+    [Fact]
+    public async Task Accept_returns_deserialized_response()
+    {
+        var api = new RecordingApi
+        {
+            Response = new QueryAcceptanceResponseDto
+            {
+                QueryId = 42,
+                Status = "Accepted",
+                Signature = new QuerySignatureRefDto { Id = 9, EstimateId = 5, Type = "Pro" },
+            },
+        };
+        var client = new FrontOfficeApiClient(api, "https://business.example/api/v1/");
+
+        var response = await client.AcceptQueryAsync("Rdv", 42, SampleBody());
+
+        Assert.Equal(42, response.QueryId);
+        Assert.Equal("Accepted", response.Status);
+        Assert.NotNull(response.Signature);
+        Assert.Equal("Pro", response.Signature!.Type);
+    }
+
+    [Fact]
+    public async Task Accept_rejects_invalid_arguments()
+    {
+        var api = new RecordingApi();
+        var client = new FrontOfficeApiClient(api, "https://business.example/api/v1/");
+
+        await Assert.ThrowsAsync<ArgumentException>(() => client.AcceptQueryAsync("", 42, SampleBody()));
+        await Assert.ThrowsAsync<ArgumentOutOfRangeException>(() => client.AcceptQueryAsync("Rdv", 0, SampleBody()));
+        await Assert.ThrowsAsync<ArgumentNullException>(() => client.AcceptQueryAsync("Rdv", 42, null!));
+        await Assert.ThrowsAsync<ArgumentException>(() => client.RejectQueryAsync("", 42));
+        await Assert.ThrowsAsync<ArgumentOutOfRangeException>(() => client.RejectQueryAsync("Rdv", 0));
+    }
+
+    private sealed class RecordingApi : IYavscApiClient
+    {
+        public HttpClient Http { get; } = new();
+        public HttpMethod? LastMethod { get; private set; }
+        public string? LastPath { get; private set; }
+        public object? LastBody { get; private set; }
+        public QueryAcceptanceResponseDto? Response { get; set; }
+
+        public Task<T> CallAsync<T>(HttpMethod method, string path, object? body = null, CancellationToken ct = default)
+        {
+            LastMethod = method;
+            LastPath = path;
+            LastBody = body;
+
+            var response = Response ?? new QueryAcceptanceResponseDto();
+            return Task.FromResult((T)(object)response);
+        }
+
+        public Task CallAsync(HttpMethod method, string path, object? body = null, CancellationToken ct = default)
+        {
+            LastMethod = method;
+            LastPath = path;
+            LastBody = body;
+            return Task.CompletedTask;
+        }
+
+        public Task<T> CallAsync<T>(HttpMethod method, string path, Func<HttpContent> contentFactory, CancellationToken ct = default)
+            => CallAsync<T>(method, path, (object?)null, ct);
+
+        public Task CallAsync(HttpMethod method, string path, Func<HttpContent> contentFactory, CancellationToken ct = default)
+            => CallAsync(method, path, (object?)null, ct);
+
+        public ValueTask DisposeAsync() => ValueTask.CompletedTask;
+    }
+}

src/PostIt/PostIt/Controls/SignaturePadView.axaml

@@ -0,0 +1,28 @@
+<UserControl xmlns="https://github.com/avaloniaui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:controls="using:PostIt.Controls"
+             x:Class="PostIt.Controls.SignaturePadView"
+             HorizontalAlignment="Stretch"
+             VerticalAlignment="Stretch">
+    <!--
+        Capture surface. The SignaturePadControl is render-agnostic,
+        so we host it inside a Border that is the capture area, and
+        overlay a Canvas for the visual feedback. The code-behind
+        repaints the canvas on every RedrawRequested. The Border size
+        is driven by the CaptureWidth / CaptureHeight styled properties.
+    -->
+    <Border x:Name="PadFrame"
+            BorderBrush="Black"
+            BorderThickness="1"
+            Background="White"
+            HorizontalAlignment="Left"
+            VerticalAlignment="Top"
+            ClipToBounds="True">
+        <Grid>
+            <controls:SignaturePadControl x:Name="InnerPad" />
+            <Canvas x:Name="InkLayer"
+                    Background="Transparent"
+                    IsHitTestVisible="False" />
+        </Grid>
+    </Border>
+</UserControl>

src/PostIt/PostIt/Controls/SignaturePadView.axaml.cs

@@ -0,0 +1,168 @@
+using System;
+using System.Collections.Generic;
+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Controls.Shapes;
+using Avalonia.Media;
+using PostIt.Models;
+
+namespace PostIt.Controls;
+
+/// <summary>
+/// Reusable signature-capture surface: wraps the render-agnostic
+/// <see cref="SignaturePadControl"/> in a sized <see cref="Border"/>
+/// (the hit-test region) with an overlay <see cref="Canvas"/> that
+/// the code-behind repaints from the control's stroke buffer. Owns
+/// the ink-rendering logic so every page that captures a signature
+/// (the dev-only <c>SignaturePage</c>, the estimate validation page,
+/// ...) shares one implementation.
+///
+/// Hosts bind <see cref="CaptureWidth"/>/<see cref="CaptureHeight"/>
+/// (DIPs, defaults 600×200) to size the surface. View models attach
+/// to the inner <see cref="SignaturePad"/> control (exposed here) to
+/// read snapshots, drive <c>Clear</c>, and subscribe to
+/// <see cref="SignaturePadControl.StrokeCompleted"/> /
+/// <see cref="SignaturePadControl.RedrawRequested"/> — the same
+/// contract the headless tests use, since a <see cref="UserControl"/>
+/// needs its XAML loaded to be drivable.
+/// </summary>
+public partial class SignaturePadView : UserControl
+{
+    private static readonly IBrush StrokeBrush = new SolidColorBrush(Color.FromRgb(0x10, 0x10, 0x10));
+    private const double StrokeThickness = 2.0;
+    private const double CoordinateMax = 10_000.0;
+
+    public static readonly StyledProperty<double> CaptureWidthProperty =
+        AvaloniaProperty.Register<SignaturePadView, double>(nameof(CaptureWidth), 600);
+
+    public static readonly StyledProperty<double> CaptureHeightProperty =
+        AvaloniaProperty.Register<SignaturePadView, double>(nameof(CaptureHeight), 200);
+
+    public double CaptureWidth
+    {
+        get => GetValue(CaptureWidthProperty);
+        set => SetValue(CaptureWidthProperty, value);
+    }
+
+    public double CaptureHeight
+    {
+        get => GetValue(CaptureHeightProperty);
+        set => SetValue(CaptureHeightProperty, value);
+    }
+
+    /// <summary>
+    /// The underlying capture control. View models attach to this to
+    /// read <see cref="SignaturePadControl.Snapshot"/> / call
+    /// <see cref="SignaturePadControl.Clear"/> and subscribe to its
+    /// events; this view repaints the ink layer from the same buffer.
+    /// </summary>
+    public SignaturePadControl SignaturePad => InnerPad;
+
+    public SignaturePadView()
+    {
+        InitializeComponent();
+
+        // Wire the capture area: the Pad is the control, the
+        // surrounding Border (PadFrame) is the hit-test region. For an
+        // inline control with no template, capture wiring happens on
+        // first measure, which is guaranteed before the user can
+        // interact, so attaching here is safe.
+        InnerPad.CaptureArea = PadFrame;
+        ApplyFrameSize();
+
+        InnerPad.RedrawRequested += OnPadRedrawRequested;
+    }
+
+    protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
+    {
+        base.OnPropertyChanged(change);
+        if (change.Property == CaptureWidthProperty || change.Property == CaptureHeightProperty)
+        {
+            ApplyFrameSize();
+            Repaint();
+        }
+    }
+
+    private void ApplyFrameSize()
+    {
+        if (PadFrame is null) return;
+        PadFrame.Width = Math.Max(1, CaptureWidth);
+        PadFrame.Height = Math.Max(1, CaptureHeight);
+    }
+
+    private void OnPadRedrawRequested(object? sender, EventArgs e) => Repaint();
+
+    /// <summary>Defensive copy of the current buffer.</summary>
+    public SignaturePadData Snapshot() => InnerPad.Snapshot();
+
+    /// <summary>Forget every captured stroke.</summary>
+    public void Clear() => InnerPad.Clear();
+
+    /// <summary>Wire-format strokes, forwarded from the inner control.</summary>
+    public IReadOnlyList<int> Strokes => InnerPad.Strokes;
+
+    private void Repaint()
+    {
+        if (InkLayer is null) return;
+
+        InkLayer.Children.Clear();
+        var w = PadFrame.Bounds.Width;
+        var h = PadFrame.Bounds.Height;
+        if (w <= 0 || h <= 0) return;
+
+        var pending = InnerPad.PendingStroke;
+        var strokes = InnerPad.Strokes;
+        int sealedCount = strokes.Count - pending.Count;
+        if (sealedCount < 0)
+        {
+            sealedCount = 0;
+        }
+
+        int i = 0;
+        while (i < sealedCount)
+        {
+            int k = strokes[i];
+            if (k <= 0) break;
+            i++; // skip the length prefix
+
+            var poly = new Polyline
+            {
+                Stroke = StrokeBrush,
+                StrokeThickness = StrokeThickness,
+                StrokeLineCap = PenLineCap.Round,
+                StrokeJoin = PenLineJoin.Round,
+            };
+            var pts = new List<Point>(k);
+            for (int p = 0; p < k; p++)
+            {
+                int nx = strokes[i++];
+                int ny = strokes[i++];
+                pts.Add(new Point(nx / CoordinateMax * w, ny / CoordinateMax * h));
+            }
+            poly.Points = pts;
+            InkLayer.Children.Add(poly);
+        }
+
+        if (pending.Count > 0)
+        {
+            var poly = new Polyline
+            {
+                Stroke = StrokeBrush,
+                StrokeThickness = StrokeThickness,
+                StrokeLineCap = PenLineCap.Round,
+                StrokeJoin = PenLineJoin.Round,
+            };
+
+            var pts = new List<Point>(pending.Count / 2);
+            for (int p = 0; p < pending.Count; p += 2)
+            {
+                int nx = pending[p];
+                int ny = pending[p + 1];
+                pts.Add(new Point(nx / CoordinateMax * w, ny / CoordinateMax * h));
+            }
+
+            poly.Points = pts;
+            InkLayer.Children.Add(poly);
+        }
+    }
+}

src/PostIt/PostIt/Helpers/ServiceCollectionHelpers.cs

@@ -31,6 +31,7 @@ public static class ServiceCollectionHelpers
             () => settings.Authentication?.Authority);
         var billingClient = new BillingApiClient(api, () => settings.ApiUrl);
         var estimateClient = new EstimateApiClient(api, () => settings.ApiUrl);
+        var frontClient = new FrontOfficeApiClient(api, () => settings.ApiUrl);
         var userDirectory = new UserDirectory(userSearchClient);
         var reverseGeocoding = new NominatimReverseGeocodingService();
 
@@ -63,6 +64,7 @@ public static class ServiceCollectionHelpers
         services.AddTransient<ProviderOngoingRequestsPage>();
         services.AddTransient<EstimateEditionPage>();
         services.AddTransient<EstimateListPage>();
+        services.AddTransient<EstimateValidationPage>();
 
         // ViewModels
         services.AddSingleton(settings);
@@ -74,6 +76,7 @@ public static class ServiceCollectionHelpers
         services.AddSingleton(activityClient);
         services.AddSingleton(billingClient);
         services.AddSingleton(estimateClient);
+        services.AddSingleton(frontClient);
         services.AddSingleton<IReverseGeocodingService>(reverseGeocoding);
         services.AddSingleton<IUserDirectory>(userDirectory);
         services.AddSingleton<HomePageViewModel>();

src/PostIt/PostIt/ViewLocator.cs

@@ -55,6 +55,7 @@ public class ViewLocator : IDataTemplate
             ProviderOngoingRequestsPageViewModel => services.GetRequiredService<ProviderOngoingRequestsPage>(),
             EstimateEditionPageViewModel => services.GetRequiredService<EstimateEditionPage>(),
             EstimateListPageViewModel => services.GetRequiredService<EstimateListPage>(),
+            EstimateValidationPageViewModel => services.GetRequiredService<EstimateValidationPage>(),
             null => new TextBlock { Text = "No view for <null>" },
             _ => new TextBlock { Text = $"No view for {data.GetType().Name}" }
         };

src/PostIt/PostIt/ViewModels/Activity/EstimateListPageViewModel.cs

@@ -5,6 +5,7 @@ using System.Linq;
 using System.Net;
 using System.Net.Http;
 using System.Threading.Tasks;
+using Avalonia;
 using CommunityToolkit.Mvvm.ComponentModel;
 using CommunityToolkit.Mvvm.Input;
 using PostIt.Helpers;
@@ -32,6 +33,7 @@ public enum EstimateListPerspective
 public partial class EstimateListPageViewModel : ViewModelBase, IActionStatusViewModel
 {
     private readonly EstimateApiClient _estimateClient;
+    private readonly FrontOfficeApiClient _frontClient;
     private readonly EstimateListPerspective _perspective;
     private List<EstimateDto> _allEstimates = new();
 
@@ -83,10 +85,14 @@ public partial class EstimateListPageViewModel : ViewModelBase, IActionStatusVie
         protected set { _ = value; }
     }
 
-    public EstimateListPageViewModel(EstimateApiClient estimateClient, EstimateListPerspective perspective)
+    public EstimateListPageViewModel(
+        EstimateApiClient estimateClient,
+        EstimateListPerspective perspective,
+        FrontOfficeApiClient frontClient)
     {
         _estimateClient = estimateClient ?? throw new ArgumentNullException(nameof(estimateClient));
         _perspective = perspective;
+        _frontClient = frontClient ?? throw new ArgumentNullException(nameof(frontClient));
     }
 
     public Task InitializeAsync() => RefreshAsync();
@@ -153,4 +159,25 @@ public partial class EstimateListPageViewModel : ViewModelBase, IActionStatusVie
     private static bool ContainsInsensitive(string? value, string query)
         => !string.IsNullOrWhiteSpace(value)
            && value.Contains(query, StringComparison.OrdinalIgnoreCase);
+
+    /// <summary>
+    /// Open the estimate validation (accept/reject with signature)
+    /// page for a specific estimate. The perspective the list was
+    /// opened in is forwarded as the actor-role UI hint; the server
+    /// independently enforces the real authorization.
+    /// </summary>
+    [RelayCommand]
+    private async Task OpenEstimateAsync(EstimateDto? estimate)
+    {
+        if (estimate is null) return;
+
+        var app = (App?)Application.Current;
+        if (app is null)
+        {
+            throw new InvalidOperationException("Application PostIt indisponible.");
+        }
+
+        var vm = new EstimateValidationPageViewModel(estimate, _perspective, _frontClient);
+        await app.PushPageAsync(vm).ConfigureAwait(true);
+    }
 }

src/PostIt/PostIt/ViewModels/Activity/EstimateValidationPageViewModel.cs

@@ -0,0 +1,256 @@
+using System;
+using System.Collections.Generic;
+using System.Net.Http;
+using System.Threading.Tasks;
+using Avalonia;
+using CommunityToolkit.Mvvm.ComponentModel;
+using CommunityToolkit.Mvvm.Input;
+using PostIt.Controls;
+using PostIt.Helpers;
+using PostIt.Models;
+using Yavsc.Api.Client;
+
+namespace PostIt.ViewModels;
+
+/// <summary>
+/// Validation (accept / reject) of a single estimate, with an optional
+/// signature. Backs the estimate validation page opened from
+/// <see cref="EstimateListPageViewModel"/> for either perspective.
+///
+/// The server (<c>POST api/v1/front/query/accept</c>) resolves the
+/// caller's role from the authenticated user compared to the query's
+/// <c>PerformerId</c>/<c>ClientId</c>; the perspective passed in here
+/// is only a UI hint (the <see cref="RoleLabel"/>). The billing code
+/// sent to the server is the estimate's <see cref="EstimateDto.CommandType"/>
+/// and the query id is its <see cref="EstimateDto.CommandId"/>.
+/// </summary>
+public partial class EstimateValidationPageViewModel : ViewModelBase, IActionStatusViewModel
+{
+    private readonly EstimateDto _estimate;
+    private readonly EstimateListPerspective _perspective;
+    private readonly FrontOfficeApiClient _frontClient;
+    private SignaturePadControl? _pad;
+
+    public string Title => _estimate.Title;
+    public string Description => _estimate.Description;
+    public long EstimateId => _estimate.Id;
+    public string CommandType => _estimate.CommandType;
+    public IReadOnlyList<EstimateLineDto> Bill => _estimate.Bill;
+    public DateTime ProviderValidationDate => _estimate.ProviderValidationDate;
+    public DateTime ClientValidationDate => _estimate.ClientValidationDate;
+
+    public string RoleLabel => _perspective == EstimateListPerspective.Provider
+        ? "Vous validez en tant que prestataire"
+        : "Vous validez en tant que client";
+
+    /// <summary>
+    /// Human-readable summary of who has already validated this
+    /// estimate, shown above the signature pad.
+    /// </summary>
+    public string ValidationStateText
+    {
+        get
+        {
+            var parts = new List<string>();
+            if (ProviderValidationDate != default)
+                parts.Add($"Prestataire validé le {ProviderValidationDate.ToLocalTime():g}");
+            if (ClientValidationDate != default)
+                parts.Add($"Client validé le {ClientValidationDate.ToLocalTime():g}");
+            return parts.Count == 0 ? "Devis en attente de validation." : string.Join(" · ", parts);
+        }
+    }
+
+    /// <summary>
+    /// True when the estimate has a linked query to accept/reject.
+    /// Estimates without a <see cref="EstimateDto.CommandId"/> are
+    /// templates and cannot be validated through the front-office
+    /// endpoint.
+    /// </summary>
+    public bool HasCommand => _estimate.CommandId is not null;
+
+    [ObservableProperty]
+    public partial bool IsBusy { get; set; }
+
+    [ObservableProperty]
+    public partial string StatusMessage { get; set; } = "Prêt.";
+
+    [ObservableProperty]
+    public partial StatusNotice ActionStatus { get; set; } = StatusNotice.Info("Prêt.");
+
+    [ObservableProperty]
+    public partial int StrokeCount { get; set; }
+
+    [ObservableProperty]
+    public partial int PointCount { get; set; }
+
+    [ObservableProperty]
+    public partial bool HasSignature { get; set; }
+
+    public override bool CanNavigateNext
+    {
+        get => false;
+        protected set { _ = value; }
+    }
+
+    public override bool CanNavigatePrevious
+    {
+        get => true;
+        protected set { _ = value; }
+    }
+
+    public EstimateValidationPageViewModel(
+        EstimateDto estimate,
+        EstimateListPerspective perspective,
+        FrontOfficeApiClient frontClient)
+    {
+        _estimate = estimate ?? throw new ArgumentNullException(nameof(estimate));
+        _perspective = perspective;
+        _frontClient = frontClient ?? throw new ArgumentNullException(nameof(frontClient));
+    }
+
+    /// <summary>
+    /// Bind the page's signature pad control (the inner control of the
+    /// page's <see cref="SignaturePadView"/>). Called from the view's
+    /// code-behind once the view is in the visual tree.
+    /// </summary>
+    public void Attach(SignaturePadControl pad)
+    {
+        if (pad is null) throw new ArgumentNullException(nameof(pad));
+        Detach();
+        _pad = pad;
+        _pad.RedrawRequested += OnPadRedraw;
+        RefreshFromPad();
+    }
+
+    public void Detach()
+    {
+        if (_pad is null) return;
+        _pad.RedrawRequested -= OnPadRedraw;
+        _pad = null;
+    }
+
+    private void OnPadRedraw(object? sender, EventArgs e) => RefreshFromPad();
+
+    private void RefreshFromPad()
+    {
+        if (_pad is null) return;
+        var snap = _pad.Snapshot();
+        StrokeCount = snap.StrokeCount;
+        PointCount = snap.PointCount;
+        HasSignature = !snap.IsEmpty;
+    }
+
+    partial void OnIsBusyChanged(bool value)
+    {
+        ValidateCommand.NotifyCanExecuteChanged();
+        RejectCommand.NotifyCanExecuteChanged();
+    }
+
+    partial void OnHasSignatureChanged(bool value)
+        => ValidateCommand.NotifyCanExecuteChanged();
+
+    private bool CanValidate => !IsBusy && HasSignature && HasCommand;
+
+    private bool CanReject => !IsBusy && HasCommand;
+
+    [RelayCommand(CanExecute = nameof(CanValidate))]
+    public async Task ValidateAsync()
+    {
+        if (_estimate.CommandId is not long queryId)
+        {
+            this.SetWarningStatus("Ce devis n'est pas lié à une demande et ne peut être validé.");
+            return;
+        }
+        if (_pad is null || _pad.Snapshot().IsEmpty)
+        {
+            this.SetWarningStatus("Veuillez signer avant de valider.");
+            return;
+        }
+
+        var snap = _pad.Snapshot();
+        IsBusy = true;
+        try
+        {
+            var body = new QueryAcceptanceRequestDto
+            {
+                Strokes = snap.Strokes,
+                CoordinateMax = SignaturePadData.CoordinateMax,
+                CapturedAtUtc = DateTime.UtcNow,
+            };
+
+            await _frontClient.AcceptQueryAsync(_estimate.CommandType, queryId, body)
+                .ConfigureAwait(true);
+
+            this.SetInfoStatus("Devis validé.");
+            await GoBackAsync().ConfigureAwait(true);
+        }
+        catch (HttpRequestException ex) when (ex.StatusCode is System.Net.HttpStatusCode.Forbidden)
+        {
+            this.SetWarningStatus("Vous n'êtes pas partie à ce devis.");
+        }
+        catch (HttpRequestException ex) when (ex.StatusCode is System.Net.HttpStatusCode.BadRequest)
+        {
+            this.SetWarningStatus($"Validation refusée: {ex.Message}");
+        }
+        catch (Exception ex)
+        {
+            this.SetErrorStatus($"Erreur: {ex.Message}");
+        }
+        finally
+        {
+            IsBusy = false;
+        }
+    }
+
+    [RelayCommand(CanExecute = nameof(CanReject))]
+    public async Task RejectAsync()
+    {
+        if (_estimate.CommandId is not long queryId)
+        {
+            this.SetWarningStatus("Ce devis n'est pas lié à une demande et ne peut être refusé.");
+            return;
+        }
+
+        IsBusy = true;
+        try
+        {
+            await _frontClient.RejectQueryAsync(_estimate.CommandType, queryId)
+                .ConfigureAwait(true);
+
+            this.SetInfoStatus("Devis refusé.");
+            await GoBackAsync().ConfigureAwait(true);
+        }
+        catch (HttpRequestException ex) when (ex.StatusCode is System.Net.HttpStatusCode.Forbidden)
+        {
+            this.SetWarningStatus("Vous n'êtes pas partie à ce devis.");
+        }
+        catch (Exception ex)
+        {
+            this.SetErrorStatus($"Erreur: {ex.Message}");
+        }
+        finally
+        {
+            IsBusy = false;
+        }
+    }
+
+    [RelayCommand]
+    public void ClearSignature()
+    {
+        _pad?.Clear();
+        RefreshFromPad();
+    }
+
+    [RelayCommand]
+    private async Task BackAsync() => await GoBackAsync().ConfigureAwait(true);
+
+    private static async Task GoBackAsync()
+    {
+        var app = (App?)Application.Current;
+        if (app is null)
+        {
+            throw new InvalidOperationException("Application PostIt indisponible.");
+        }
+        await app.GoBackAsync().ConfigureAwait(true);
+    }
+}

src/PostIt/PostIt/ViewModels/Layout/HomePageViewModel.cs

@@ -90,7 +90,13 @@ public class HomePageViewModel : ViewModelBase
             throw new InvalidOperationException("Client devis indisponible.");
         }
 
-        var vm = new EstimateListPageViewModel(estimateClient, perspective);
+        var frontClient = app.ServiceProvider?.GetRequiredService<FrontOfficeApiClient>();
+        if (frontClient is null)
+        {
+            throw new InvalidOperationException("Client front-office indisponible.");
+        }
+
+        var vm = new EstimateListPageViewModel(estimateClient, perspective, frontClient);
         await vm.InitializeAsync();
         await app.PushPageAsync(vm);
     }

src/PostIt/PostIt/ViewModels/Signature/SignaturePageViewModel.cs

@@ -85,10 +85,12 @@ public partial class SignaturePageViewModel : ViewModelBase, IActionStatusViewMo
     }
 
     /// <summary>
-    /// Bind a freshly-constructed (or re-templated) control to this
-    /// VM. Called from the view's code-behind once the control has
-    /// been added to the visual tree and its template applied (so
-    /// <see cref="SignaturePadControl.CaptureArea"/> is wired).
+    /// Bind the inner <see cref="SignaturePadControl"/> of the page's
+    /// <see cref="SignaturePadView"/> to this VM. Called from the
+    /// page's code-behind once the view is in the visual tree (so the
+    /// control's <see cref="SignaturePadControl.CaptureArea"/> is
+    /// wired). Attaching to the control directly (rather than the
+    /// view) keeps the same contract the headless tests use.
     /// </summary>
     public void Attach(SignaturePadControl control)
     {

src/PostIt/PostIt/Views/Activity/EstimateListPage.axaml

@@ -29,34 +29,40 @@
                             CornerRadius="8"
                             Padding="10"
                             Margin="0,0,0,8">
-                        <Grid RowDefinitions="Auto,Auto" ColumnDefinitions="*,Auto">
-                            <TextBlock Grid.Row="0"
-                                       Grid.Column="0"
-                                       Text="{Binding Title}"
-                                       FontWeight="Bold"
-                                       TextWrapping="Wrap" />
-                            <TextBlock Grid.Row="0"
-                                       Grid.Column="1"
-                                       Text="{Binding Id}"
-                                       FontSize="11"
-                                       Opacity="0.75"
-                                       HorizontalAlignment="Right" />
+                        <StackPanel Spacing="8">
+                            <Grid RowDefinitions="Auto,Auto" ColumnDefinitions="*,Auto">
+                                <TextBlock Grid.Row="0"
+                                           Grid.Column="0"
+                                           Text="{Binding Title}"
+                                           FontWeight="Bold"
+                                           TextWrapping="Wrap" />
+                                <TextBlock Grid.Row="0"
+                                           Grid.Column="1"
+                                           Text="{Binding Id}"
+                                           FontSize="11"
+                                           Opacity="0.75"
+                                           HorizontalAlignment="Right" />
 
-                            <TextBlock Grid.Row="1"
-                                       Grid.Column="0"
-                                       Margin="0,6,0,0"
-                                       Text="{Binding Description}"
-                                       FontSize="11"
-                                       Opacity="0.75"
-                                       TextWrapping="Wrap" />
-                            <TextBlock Grid.Row="1"
-                                       Grid.Column="1"
-                                       Margin="0,6,0,0"
-                                       Text="{Binding Bill.Count}"
-                                       FontSize="11"
-                                       Opacity="0.65"
-                                       HorizontalAlignment="Right" />
-                        </Grid>
+                                <TextBlock Grid.Row="1"
+                                           Grid.Column="0"
+                                           Margin="0,6,0,0"
+                                           Text="{Binding Description}"
+                                           FontSize="11"
+                                           Opacity="0.75"
+                                           TextWrapping="Wrap" />
+                                <TextBlock Grid.Row="1"
+                                           Grid.Column="1"
+                                           Margin="0,6,0,0"
+                                           Text="{Binding Bill.Count}"
+                                           FontSize="11"
+                                           Opacity="0.65"
+                                           HorizontalAlignment="Right" />
+                            </Grid>
+                            <Button Content="Ouvrir"
+                                    HorizontalAlignment="Right"
+                                    Command="{Binding $parent[ContentPage].((vm:EstimateListPageViewModel)DataContext).OpenEstimateCommand}"
+                                    CommandParameter="{Binding}" />
+                        </StackPanel>
                     </Border>
                 </DataTemplate>
             </ListBox.ItemTemplate>

src/PostIt/PostIt/Views/Activity/EstimateValidationPage.axaml

@@ -0,0 +1,126 @@
+<ContentPage xmlns="https://github.com/avaloniaui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:vm="using:PostIt.ViewModels"
+             xmlns:controls="using:PostIt.Controls"
+             xmlns:dto="using:Yavsc.Api.Client"
+             xmlns:postitControls="using:PostIt.Controls"
+             x:Class="PostIt.Views.EstimateValidationPage"
+             x:DataType="vm:EstimateValidationPageViewModel"
+             Header="Validation du devis">
+    <Grid RowDefinitions="Auto,*,Auto" Margin="12">
+        <StackPanel Grid.Row="0" Spacing="3" Margin="0,0,0,8">
+            <TextBlock Text="{Binding Title}"
+                       FontSize="20"
+                       FontWeight="Bold"
+                       TextWrapping="Wrap" />
+            <TextBlock Text="{Binding RoleLabel}" Opacity="0.75" />
+            <TextBlock Text="{Binding ValidationStateText}"
+                       FontSize="11"
+                       Opacity="0.75"
+                       TextWrapping="Wrap" />
+        </StackPanel>
+
+        <ScrollViewer Grid.Row="1">
+            <StackPanel Spacing="10">
+                <Border BorderThickness="1"
+                        BorderBrush="#22000000"
+                        CornerRadius="8"
+                        Padding="10">
+                    <StackPanel Spacing="6">
+                        <Grid ColumnDefinitions="Auto,12,*">
+                            <TextBlock Grid.Column="0"
+                                       Text="N°"
+                                       FontWeight="SemiBold" />
+                            <TextBlock Grid.Column="2"
+                                       Text="{Binding EstimateId}" />
+                        </Grid>
+                        <Grid ColumnDefinitions="Auto,12,*">
+                            <TextBlock Grid.Column="0"
+                                       Text="Type"
+                                       FontWeight="SemiBold" />
+                            <TextBlock Grid.Column="2"
+                                       Text="{Binding CommandType}" />
+                        </Grid>
+                        <TextBlock Text="{Binding Description}"
+                                   TextWrapping="Wrap"
+                                   Opacity="0.85" />
+                    </StackPanel>
+                </Border>
+
+                <Border BorderThickness="1"
+                        BorderBrush="#22000000"
+                        CornerRadius="8"
+                        Padding="10">
+                    <StackPanel Spacing="8">
+                        <TextBlock Text="Lignes du devis" FontWeight="SemiBold" />
+                        <ItemsControl ItemsSource="{Binding Bill}">
+                            <ItemsControl.ItemTemplate>
+                                <DataTemplate x:DataType="dto:EstimateLineDto">
+                                    <Grid ColumnDefinitions="*,8,60,8,120" Margin="0,0,0,4">
+                                        <TextBlock Grid.Column="0"
+                                                   Text="{Binding Name}"
+                                                   TextWrapping="Wrap" />
+                                        <TextBlock Grid.Column="2"
+                                                   Text="{Binding Count}"
+                                                   HorizontalAlignment="Right" />
+                                        <StackPanel Grid.Column="4"
+                                                    Orientation="Horizontal"
+                                                    HorizontalAlignment="Right"
+                                                    Spacing="4">
+                                            <TextBlock Text="{Binding UnitaryCost, StringFormat='{}{0:N2}'}" />
+                                            <TextBlock Text="{Binding Currency}" Opacity="0.7" />
+                                        </StackPanel>
+                                    </Grid>
+                                </DataTemplate>
+                            </ItemsControl.ItemTemplate>
+                        </ItemsControl>
+                    </StackPanel>
+                </Border>
+
+                <Border BorderThickness="1"
+                        BorderBrush="#22000000"
+                        CornerRadius="8"
+                        Padding="10">
+                    <StackPanel Spacing="8">
+                        <TextBlock Text="Signature" FontWeight="SemiBold" />
+                        <TextBlock Text="Signez ci-dessous pour valider ce devis."
+                                   FontSize="11"
+                                   Opacity="0.7" />
+                        <controls:SignaturePadView x:Name="Pad"
+                                                   CaptureWidth="560"
+                                                   CaptureHeight="200" />
+                        <TextBlock FontSize="11"
+                                   Foreground="DarkSlateGray">
+                            <Run Text="Traits: " />
+                            <Run Text="{Binding StrokeCount, Mode=OneWay}" />
+                            <Run Text="  ·  Points: " />
+                            <Run Text="{Binding PointCount, Mode=OneWay}" />
+                        </TextBlock>
+                    </StackPanel>
+                </Border>
+            </StackPanel>
+        </ScrollViewer>
+
+        <Grid Grid.Row="2" ColumnDefinitions="Auto,*,Auto" Margin="0,12,0,0">
+            <StackPanel Grid.Column="0" Orientation="Horizontal" Spacing="8">
+                <Button Content="Effacer"
+                        Command="{Binding ClearSignatureCommand}" />
+                <Button Content="Valider"
+                        Command="{Binding ValidateCommand}" />
+                <Button Content="Refuser"
+                        Command="{Binding RejectCommand}" />
+                <Button Content="Retour"
+                        Command="{Binding BackCommand}" />
+            </StackPanel>
+            <StackPanel Grid.Column="2"
+                        Orientation="Horizontal"
+                        Spacing="8"
+                        VerticalAlignment="Center">
+                <ProgressBar Width="120"
+                             IsIndeterminate="True"
+                             IsVisible="{Binding IsBusy}" />
+                <postitControls:StatusBar DataContext="{Binding ActionStatus}" />
+            </StackPanel>
+        </Grid>
+    </Grid>
+</ContentPage>

src/PostIt/PostIt/Views/Activity/EstimateValidationPage.axaml.cs

@@ -0,0 +1,32 @@
+using Avalonia.Controls;
+using PostIt.Controls;
+using PostIt.ViewModels;
+
+namespace PostIt.Views;
+
+public partial class EstimateValidationPage : ContentPage
+{
+    private EstimateValidationPageViewModel? _vm;
+
+    public EstimateValidationPage()
+    {
+        InitializeComponent();
+
+        DataContextChanged += (_, _) => RebindViewModel(DataContext as EstimateValidationPageViewModel);
+        Unloaded += (_, _) => _vm?.Detach();
+    }
+
+    private void RebindViewModel(EstimateValidationPageViewModel? vm)
+    {
+        if (_vm is not null)
+        {
+            _vm.Detach();
+        }
+
+        _vm = vm;
+
+        if (_vm is null || Pad is null) return;
+
+        _vm.Attach(Pad.SignaturePad);
+    }
+}

src/PostIt/PostIt/Views/Signature/SignaturePage.axaml

@@ -29,29 +29,15 @@
                    FontWeight="Bold" />
 
         <!--
-            Capture surface. The SignaturePadControl is render-
-            agnostic, so we host it inside a fixed-size Border
-            that is the PART_CaptureArea, and overlay a Canvas
-            for the visual feedback. The view's code-behind
-            repaints the canvas on every RedrawRequested.
+            Capture surface. SignaturePadView owns the SignaturePadControl,
+            the capture-area Border, the ink overlay canvas, and the
+            repaint logic; the page just sizes it from the VM and reads
+            the captured data through the view's API.
         -->
-        <Border Grid.Row="1"
-                x:Name="PadFrame"
-                Width="{Binding Width}"
-                Height="{Binding Height}"
-                BorderBrush="Black"
-                BorderThickness="1"
-                Background="White"
-                HorizontalAlignment="Left"
-                VerticalAlignment="Top"
-                ClipToBounds="True">
-            <Grid>
-                <controls:SignaturePadControl x:Name="Pad" />
-                <Canvas x:Name="InkLayer"
-                        Background="Transparent"
-                        IsHitTestVisible="False" />
-            </Grid>
-        </Border>
+        <controls:SignaturePadView Grid.Row="1"
+                                   x:Name="Pad"
+                                   CaptureWidth="{Binding Width}"
+                                   CaptureHeight="{Binding Height}" />
 
         <StackPanel Grid.Row="2"
                     Orientation="Horizontal"

src/PostIt/PostIt/Views/Signature/SignaturePage.axaml.cs

@@ -1,9 +1,4 @@
-using System;
-using System.Collections.Generic;
-using Avalonia;
 using Avalonia.Controls;
-using Avalonia.Controls.Shapes;
-using Avalonia.Media;
 using PostIt.Controls;
 using PostIt.ViewModels;
 
@@ -11,26 +6,15 @@ namespace PostIt.Views;
 
 public partial class SignaturePage : ContentPage
 {
-    private static readonly IBrush StrokeBrush = new SolidColorBrush(Color.FromRgb(0x10, 0x10, 0x10));
-    private const double StrokeThickness = 2.0;
-    private const double CoordinateMax = 10_000.0;
-
     private SignaturePageViewModel? _vm;
-    private SignaturePadControl? _control;
 
     public SignaturePage()
     {
         InitializeComponent();
 
-        // Wire the capture area: the Pad itself is the control, the
-        // surrounding Border (PadFrame) is the hit-test region. We
-        // set CaptureArea once the control's template has been
-        // applied — for an inline control with no template, that
-        // happens on first measure, which is guaranteed before
-        // the user can interact, so attaching here is safe.
-        _control = Pad;
-        _control.CaptureArea = PadFrame;
-
+        // SignaturePadView owns the capture area wiring and the ink
+        // repaint; the page only forwards the view to the VM so it can
+        // read snapshots / subscribe to stroke events.
         DataContextChanged += (_, _) => RebindViewModel(DataContext as SignaturePageViewModel);
     }
 
@@ -39,82 +23,12 @@ public partial class SignaturePage : ContentPage
         if (_vm is not null)
         {
             _vm.Detach();
-            _control!.RedrawRequested -= OnRedrawRequested;
         }
 
         _vm = vm;
 
-        if (_vm is null || _control is null) return;
+        if (_vm is null || Pad is null) return;
 
-        _vm.Attach(_control);
-        _control.RedrawRequested += OnRedrawRequested;
-        Repaint();
+        _vm.Attach(Pad.SignaturePad);
     }
-
-    private void OnRedrawRequested(object? sender, EventArgs e) => Repaint();
-
-    private void Repaint()
-    {
-        if (_control is null || InkLayer is null) return;
-
-        InkLayer.Children.Clear();
-        var w = PadFrame.Bounds.Width;
-        var h = PadFrame.Bounds.Height;
-        if (w <= 0 || h <= 0) return;
-
-        var pending = _control.PendingStroke;
-        var strokes = _control.Strokes;
-        int sealedCount = strokes.Count - pending.Count;
-        if (sealedCount < 0)
-        {
-            sealedCount = 0;
-        }
-
-        int i = 0;
-        while (i < sealedCount)
-        {
-            int k = strokes[i];
-            if (k <= 0) break;
-            i++; // skip the length prefix
-
-            var poly = new Polyline
-            {
-                Stroke = StrokeBrush,
-                StrokeThickness = StrokeThickness,
-                StrokeLineCap = PenLineCap.Round,
-                StrokeJoin = PenLineJoin.Round,
-            };
-            var pts = new List<Point>(k);
-            for (int p = 0; p < k; p++)
-            {
-                int nx = strokes[i++];
-                int ny = strokes[i++];
-                pts.Add(new Point(nx / CoordinateMax * w, ny / CoordinateMax * h));
-            }
-            poly.Points = pts;
-            InkLayer.Children.Add(poly);
-        }
-
-        if (pending.Count > 0)
-        {
-            var poly = new Polyline
-            {
-                Stroke = StrokeBrush,
-                StrokeThickness = StrokeThickness,
-                StrokeLineCap = PenLineCap.Round,
-                StrokeJoin = PenLineJoin.Round,
-            };
-
-            var pts = new List<Point>(pending.Count / 2);
-            for (int p = 0; p < pending.Count; p += 2)
-            {
-                int nx = pending[p];
-                int ny = pending[p + 1];
-                pts.Add(new Point(nx / CoordinateMax * w, ny / CoordinateMax * h));
-            }
-
-            poly.Points = pts;
-            InkLayer.Children.Add(poly);
-        }
-    }
-}
+}

src/Yavsc.Api.Client/Dtos/QueryAcceptanceDto.cs

@@ -0,0 +1,44 @@
+using System;
+
+namespace Yavsc.Api.Client;
+
+/// <summary>
+/// Body of <c>POST api/v1/front/query/accept</c> and
+/// <c>.../query/reject</c>, mirroring the server-side
+/// <c>Yavsc.ViewModels.FrontOffice.QueryAcceptanceRequest</c>.
+/// <see cref="Strokes"/> is optional: when non-empty on accept it is
+/// the PostIt wire-format signature captured with the acceptance; null
+/// or empty means no signature (the only valid value on reject).
+/// </summary>
+public sealed class QueryAcceptanceRequestDto
+{
+    public int[]? Strokes { get; set; }
+
+    public int CoordinateMax { get; set; } = 10_000;
+
+    public DateTime? CapturedAtUtc { get; set; }
+}
+
+/// <summary>
+/// Response of <c>POST .../query/accept</c> / <c>.../query/reject</c>
+/// (<c>Ok(new { queryId, status, signature = ... })</c>). The
+/// <see cref="Signature"/> ref is non-null only when a signature was
+/// staged on accept.
+/// </summary>
+public sealed class QueryAcceptanceResponseDto
+{
+    public long QueryId { get; set; }
+
+    public string? Status { get; set; }
+
+    public QuerySignatureRefDto? Signature { get; set; }
+}
+
+public sealed class QuerySignatureRefDto
+{
+    public long Id { get; set; }
+
+    public long EstimateId { get; set; }
+
+    public string? Type { get; set; }
+}

src/Yavsc.Api.Client/FrontOfficeApiClient.cs

@@ -0,0 +1,108 @@
+using System;
+using System.Net.Http;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace Yavsc.Api.Client;
+
+/// <summary>
+/// HTTP client for the front-office query routes
+/// (<c>api/v1/front/query/accept</c> / <c>.../reject</c>, served by
+/// <see cref="Yavsc.ApiControllers.FrontOfficeApiController"/>). Same
+/// DTO↔path mapper shape as <see cref="EstimateApiClient"/>: transport
+/// (base URL, JSON, Bearer auth, silent refresh on 401) is delegated
+/// to <see cref="IYavscApiClient"/>.
+///
+/// The server resolves the caller's role (provider vs client vs admin)
+/// from the authenticated user compared to the query's
+/// <c>PerformerId</c>/<c>ClientId</c>; the client does not declare a
+/// role. <paramref name="billingCode"/> is the estimate's
+/// <see cref="EstimateDto.CommandType"/> and <paramref name="queryId"/>
+/// is its <see cref="EstimateDto.CommandId"/>.
+/// </summary>
+public sealed class FrontOfficeApiClient
+{
+    private const string PathPrefix = "front";
+
+    private readonly IYavscApiClient _api;
+    private readonly Func<string> _businessBaseAddress;
+
+    public FrontOfficeApiClient(IYavscApiClient api, string businessBaseAddress)
+        : this(api, () => businessBaseAddress)
+    {
+    }
+
+    public FrontOfficeApiClient(IYavscApiClient api, Func<string> businessBaseAddress)
+    {
+        _api = api ?? throw new ArgumentNullException(nameof(api));
+        _businessBaseAddress = businessBaseAddress ?? throw new ArgumentNullException(nameof(businessBaseAddress));
+        _ = ResolveBusinessBaseAddress();
+    }
+
+    /// <summary>
+    /// Accept (validate) the query <paramref name="queryId"/> under
+    /// billing code <paramref name="billingCode"/>. When
+    /// <paramref name="body"/> carries a non-empty signature, the
+    /// server stages it on the query's linked estimate and stamps the
+    /// matching validation date.
+    /// </summary>
+    public async Task<QueryAcceptanceResponseDto> AcceptQueryAsync(
+        string billingCode,
+        long queryId,
+        QueryAcceptanceRequestDto body,
+        CancellationToken ct = default)
+    {
+        if (string.IsNullOrWhiteSpace(billingCode))
+            throw new ArgumentException("billingCode is required.", nameof(billingCode));
+        if (queryId <= 0)
+            throw new ArgumentOutOfRangeException(nameof(queryId));
+        if (body is null)
+            throw new ArgumentNullException(nameof(body));
+
+        var path = $"{PathPrefix}/query/accept?billingCode={Uri.EscapeDataString(billingCode)}&queryId={queryId}";
+        var response = await _api.CallAsync<QueryAcceptanceResponseDto>(
+            HttpMethod.Post,
+            Absolute(path),
+            body: body,
+            ct: ct).ConfigureAwait(false);
+
+        return response ?? new QueryAcceptanceResponseDto { QueryId = queryId };
+    }
+
+    /// <summary>
+    /// Reject the query <paramref name="queryId"/> under billing code
+    /// <paramref name="billingCode"/>. A signature is not meaningful on
+    /// a rejection; the server refuses one with 400, so this sends no
+    /// body.
+    /// </summary>
+    public async Task<QueryAcceptanceResponseDto> RejectQueryAsync(
+        string billingCode,
+        long queryId,
+        CancellationToken ct = default)
+    {
+        if (string.IsNullOrWhiteSpace(billingCode))
+            throw new ArgumentException("billingCode is required.", nameof(billingCode));
+        if (queryId <= 0)
+            throw new ArgumentOutOfRangeException(nameof(queryId));
+
+        var path = $"{PathPrefix}/query/reject?billingCode={Uri.EscapeDataString(billingCode)}&queryId={queryId}";
+        var response = await _api.CallAsync<QueryAcceptanceResponseDto>(
+            HttpMethod.Post,
+            Absolute(path),
+            body: null,
+            ct: ct).ConfigureAwait(false);
+
+        return response ?? new QueryAcceptanceResponseDto { QueryId = queryId };
+    }
+
+    private string Absolute(string relativePath) => new Uri(ResolveBusinessBaseAddress(), relativePath).ToString();
+
+    private Uri ResolveBusinessBaseAddress()
+    {
+        var raw = _businessBaseAddress();
+        if (string.IsNullOrWhiteSpace(raw))
+            throw new InvalidOperationException("Business base address is required.");
+
+        return new Uri(raw, UriKind.Absolute);
+    }
+}