fix(client-controller): single constructor with IHtmlLocalizer

The partial class ClientController had two constructors declared
across ClientController.cs and ClientController.Collections.cs.
ASP.NET Core DI failed to pick one at request time with:

  System.InvalidOperationException: Multiple constructors accepting
  all given argument types have been found in type
  'Yavsc.Controllers.ClientController'.

Move IHtmlLocalizer<ClientController> into the primary constructor
in ClientController.cs and drop the duplicate one in
ClientController.Collections.cs. The Collections partial now keeps
only its readonly field and action methods; the constructor and
field assignment are unified on the main file.

Also add the missing 'using Microsoft.AspNetCore.Mvc.Localization;'
to ClientController.cs so IHtmlLocalizer resolves.

src/Yavsc.Org.Tests/StaticAssetsPathsTests.cs

@@ -0,0 +1,62 @@
+using System.IO;
+using Xunit;
+using Xunit.v3;
+
+namespace Yavsc.Org.Tests;
+
+/// <summary>
+/// Diagnostic-only test that confirms the static-assets manifests
+/// the WebServerFixture relies on are present in the test bin.
+///
+/// The MSBuild target <c>CopyYavscOrgStaticAssets</c> in
+/// Yavsc.Org.Tests.csproj mirrors the Yavsc.Org static-assets
+/// manifests (<c>Yavsc.Org.staticwebassets.endpoints.json</c> and
+/// <c>Yavsc.Org.staticwebassets.runtime.json</c>) from
+/// <c>../Yavsc.Org/bin/$(Configuration)/$(TargetFramework)/</c> into
+/// the test output directory. The fixture then calls
+/// <c>_app.MapStaticAssets(testRuntimeManifest)</c> with the
+/// <c>runtime.json</c> path so the test host resolves the manifest
+/// explicitly by file location, bypassing the default
+/// {AssemblyName}.staticwebassets.* lookup (which would look for
+/// <c>Yavsc.Org.Tests.staticwebassets.*</c>, files we don't produce).
+///
+/// This test is a guard for that build-time copy: if it ever fails
+/// or is removed, the WebServerFixture will throw
+/// "The static resources manifest file ... was not found" at boot.
+/// Once the WebServerFixture is stable in CI, this test can be
+/// deleted.
+/// </summary>
+public class StaticAssetsPathsTests
+{
+    private readonly ITestOutputHelper _output;
+
+    public StaticAssetsPathsTests(ITestOutputHelper output)
+    {
+        _output = output;
+    }
+
+    [Fact]
+    public void YavscOrg_staticwebassets_manifests_are_mirrored_into_test_bin()
+    {
+        var testBin = AppContext.BaseDirectory;
+        _output.WriteLine($"Test bin (AppContext.BaseDirectory) = {testBin}");
+
+        var runtimeManifest = Path.Combine(testBin,
+            "Yavsc.Org.staticwebassets.runtime.json");
+        var endpointsManifest = Path.Combine(testBin,
+            "Yavsc.Org.staticwebassets.endpoints.json");
+
+        _output.WriteLine($"runtime manifest:   exists = {File.Exists(runtimeManifest)}, path = {runtimeManifest}");
+        _output.WriteLine($"endpoints manifest: exists = {File.Exists(endpointsManifest)}, path = {endpointsManifest}");
+
+        Assert.True(File.Exists(runtimeManifest),
+            $"Expected {runtimeManifest} to be copied by CopyYavscOrgStaticAssets, but it is missing. " +
+            "Check that the Yavsc.Org project builds before Yavsc.Org.Tests so the source manifest exists " +
+            "and that the <Target> in Yavsc.Org.Tests.csproj is wired up correctly.");
+
+        Assert.True(File.Exists(endpointsManifest),
+            $"Expected {endpointsManifest} to be copied by CopyYavscOrgStaticAssets, but it is missing. " +
+            "The runtime manifest alone is not enough — MapStaticAssets() may also read the endpoints " +
+            "manifest depending on the SDK version.");
+    }
+}