feat(installer): add WPF installer/configurator project

Standalone WPF app (ClaudeDo.Installer) that handles full installation
and ongoing configuration of ClaudeDo. Two modes: wizard for first run,
tabbed settings panel for subsequent launches. Page-based extensibility
via IInstallerPage interface — adding new config sections requires only
one new class.

Install pipeline: dotnet publish, deploy binaries, write configs, init
DB (via SchemaInitializer from ClaudeDo.Data), register Windows Service,
create shortcuts. Dark theme matching the Avalonia app (forest teal accent).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/ClaudeDo.Installer/Pages/UiSettingsPage/UiSettingsPageViewModel.cs

@@ -0,0 +1,83 @@
+using System.Windows.Controls;
+using ClaudeDo.Installer.Core;
+using CommunityToolkit.Mvvm.ComponentModel;
+
+namespace ClaudeDo.Installer.Pages.UiSettingsPage;
+
+public partial class UiSettingsPageViewModel : ObservableObject, IInstallerPage
+{
+    private readonly InstallContext _context;
+    private UiSettingsPageView? _view;
+
+    public string Title => "UI Settings";
+    public string Icon => "\uE771";
+    public int Order => 3;
+    public bool ShowInWizard => true;
+    public bool ShowInSettings => true;
+    public UserControl View => _view ??= new UiSettingsPageView { DataContext = this };
+
+    [ObservableProperty] private string _signalRUrl = "http://127.0.0.1:47821/hub";
+    [ObservableProperty] private string _uiDbPath = "~/.todo-app/todo.db";
+    [ObservableProperty] private bool _isSynced = true;
+    [ObservableProperty] private string? _validationError;
+
+    public UiSettingsPageViewModel(InstallContext context) => _context = context;
+
+    partial void OnIsSyncedChanged(bool value)
+    {
+        if (value) SyncFromContext();
+    }
+
+    private void SyncFromContext()
+    {
+        SignalRUrl = $"http://127.0.0.1:{_context.SignalRPort}/hub";
+        UiDbPath = _context.DbPath;
+    }
+
+    public Task LoadAsync()
+    {
+        if (IsSynced)
+        {
+            SyncFromContext();
+        }
+        else
+        {
+            var cfg = InstallerAppSettings.Load();
+            SignalRUrl = cfg.SignalRUrl;
+            UiDbPath = cfg.DbPath;
+        }
+        return Task.CompletedTask;
+    }
+
+    public Task ApplyAsync()
+    {
+        if (IsSynced) SyncFromContext();
+        _context.SignalRUrl = SignalRUrl;
+        _context.UiDbPath = UiDbPath;
+        return Task.CompletedTask;
+    }
+
+    public bool Validate()
+    {
+        if (string.IsNullOrWhiteSpace(SignalRUrl))
+        {
+            ValidationError = "SignalR URL is required.";
+            return false;
+        }
+
+        if (string.IsNullOrWhiteSpace(UiDbPath))
+        {
+            ValidationError = "Database path is required.";
+            return false;
+        }
+
+        if (!Uri.TryCreate(SignalRUrl, UriKind.Absolute, out _))
+        {
+            ValidationError = "SignalR URL must be a valid URL.";
+            return false;
+        }
+
+        ValidationError = null;
+        return true;
+    }
+}