feat(postit): persist call IP privacy preference

Store HideIpAddressInCalls on user accounts, expose it in the profile API and PostIt editor, and preserve preferences for older clients. Add the EF migration, regression tests and architecture documentation.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/PostIt/PostIt.Tests/AdministrationAccessTests.cs

@@ -180,6 +180,60 @@ public class AdministrationAccessTests
         Assert.Contains("Impossible de charger mon usage", vm.UsageError);
     }
 
+    [Theory]
+    [InlineData(false)]
+    [InlineData(true)]
+    public async Task My_profile_loads_and_includes_the_call_privacy_preference_in_the_save_payload(bool initial)
+    {
+        await using var api = new ProfileTransport("Performer") { HideIpAddressInCalls = initial };
+        var vm = new UserProfilePageViewModel(api);
+        await vm.RefreshAsync();
+        Assert.Equal(initial, vm.HideIpAddressInCalls);
+        vm.HideIpAddressInCalls = !initial;
+        Assert.Equal(!initial, vm.BuildProfileUpdateRequest().HideIpAddressInCalls);
+        Assert.True(vm.SaveProfileCommand.CanExecute(null));
+        Assert.True(vm.IsProfileLoaded);
+    }
+
+    [AvaloniaFact]
+    public async Task My_profile_privacy_checkbox_is_two_way_and_disabled_before_loading()
+    {
+        await using var api = new ProfileTransport("Performer") { HideIpAddressInCalls = true };
+        var vm = new UserProfilePageViewModel(api);
+        var page = new UserProfilePage { DataContext = vm };
+        var window = new Window { Content = page };
+        try
+        {
+            window.Show();
+            var checkbox = Assert.Single(page.GetVisualDescendants().OfType<CheckBox>(),
+                control => Equals(control.Content, "Masquer mon adresse IP aux autres participants"));
+            Assert.False(checkbox.IsEffectivelyEnabled);
+            await vm.RefreshAsync();
+            Assert.True(checkbox.IsEffectivelyEnabled);
+            Assert.True(checkbox.IsChecked);
+            checkbox.IsChecked = false;
+            Assert.False(vm.HideIpAddressInCalls);
+            Assert.Equal(false, vm.BuildProfileUpdateRequest().HideIpAddressInCalls);
+            vm.IsBusy = true;
+            Assert.False(checkbox.IsEffectivelyEnabled);
+        }
+        finally
+        {
+            window.Close();
+        }
+    }
+
+    [Fact]
+    public async Task Profile_read_failure_prevents_saving_a_default_call_privacy_preference()
+    {
+        await using var api = new ProfileTransport("Performer") { FailProfile = true };
+        var vm = new UserProfilePageViewModel(api);
+        await vm.RefreshAsync();
+        Assert.False(vm.IsProfileLoaded);
+        Assert.False(vm.SaveProfileCommand.CanExecute(null));
+        Assert.Contains("Impossible de charger le profil", vm.StatusMessage);
+    }
+
     internal sealed class ProfileTransport : YavscApiClient
     {
         private readonly string _tokenPath;
@@ -188,6 +242,7 @@ public class AdministrationAccessTests
         public Task<Me>? PendingProfile { get; set; }
         public bool FailProfile { get; set; }
         public bool FailUsage { get; set; }
+        public bool HideIpAddressInCalls { get; set; }
         public ResourceUsageApiClient UsageClient => new(this, Settings.ApiUrl);
 
         public ProfileTransport(string role)
@@ -216,7 +271,7 @@ public class AdministrationAccessTests
                 if (FailProfile)
                     throw new HttpRequestException("Profile unavailable");
                 result = PendingProfile is not null ? await PendingProfile
-                    : new Me { UserId = "alice-id", UserName = "alice", Roles = [_role] };
+                    : new Me { UserId = "alice-id", UserName = "alice", Roles = [_role], HideIpAddressInCalls = HideIpAddressInCalls };
             }
             else if (path.Contains("/resource-usage/"))
             {