feat(i18n): add WPF localization primitives and Language config to installer

src/ClaudeDo.Installer/ClaudeDo.Installer.csproj

@@ -46,6 +46,9 @@
   <ItemGroup>
     <ProjectReference Include="..\ClaudeDo.Data\ClaudeDo.Data.csproj" />
     <ProjectReference Include="..\ClaudeDo.Releases\ClaudeDo.Releases.csproj" />
+    <ProjectReference Include="..\ClaudeDo.Localization\ClaudeDo.Localization.csproj" />
   </ItemGroup>
 
+  <Import Project="..\ClaudeDo.Localization\Locales.targets" />
+
 </Project>

src/ClaudeDo.Installer/Core/ConfigModels.cs

@@ -77,6 +77,7 @@ public sealed class InstallerAppSettings
 {
     public string DbPath { get; set; } = "~/.todo-app/todo.db";
     public string SignalRUrl { get; set; } = "http://127.0.0.1:47821/hub";
+    public string Language { get; set; } = "";
 
     private static readonly JsonSerializerOptions ReadOpts = new()
     {

src/ClaudeDo.Installer/Localization/LocalizedString.cs

@@ -0,0 +1,22 @@
+using System.ComponentModel;
+using ClaudeDo.Localization;
+
+namespace ClaudeDo.Installer.Localization;
+
+public sealed class LocalizedString : INotifyPropertyChanged
+{
+    private readonly ILocalizer _localizer;
+    private readonly string _key;
+
+    public LocalizedString(ILocalizer localizer, string key)
+    {
+        _localizer = localizer;
+        _key = key;
+        _localizer.LanguageChanged += (_, _) =>
+            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(Value)));
+    }
+
+    public string Value => _localizer[_key];
+
+    public event PropertyChangedEventHandler? PropertyChanged;
+}

src/ClaudeDo.Installer/Localization/TrExtension.cs

@@ -0,0 +1,27 @@
+using System;
+using System.Windows.Data;
+using System.Windows.Markup;
+using ClaudeDo.Localization;
+
+namespace ClaudeDo.Installer.Localization;
+
+public sealed class TrExtension : MarkupExtension
+{
+    public TrExtension() { }
+    public TrExtension(string key) => Key = key;
+
+    public string Key { get; set; } = "";
+
+    public static ILocalizer? Localizer { get; set; }
+
+    public override object ProvideValue(IServiceProvider serviceProvider)
+    {
+        var loc = Localizer ?? throw new InvalidOperationException("TrExtension.Localizer not initialized");
+        var binding = new Binding(nameof(LocalizedString.Value))
+        {
+            Source = new LocalizedString(loc, Key),
+            Mode = BindingMode.OneWay
+        };
+        return binding.ProvideValue(serviceProvider);
+    }
+}