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/Core/InstallContext.cs

@@ -0,0 +1,30 @@
+namespace ClaudeDo.Installer.Core;
+
+public sealed class InstallContext
+{
+    // WelcomePage
+    public string SourceDirectory { get; set; } = "";
+    public string InstallDirectory { get; set; } = @"C:\Program Files\ClaudeDo";
+
+    // PathsPage
+    public string DbPath { get; set; } = "~/.todo-app/todo.db";
+    public string LogRoot { get; set; } = "~/.todo-app/logs";
+    public string SandboxRoot { get; set; } = "~/.todo-app/sandbox";
+    public string WorktreeRootStrategy { get; set; } = "sibling";
+    public string CentralWorktreeRoot { get; set; } = "~/.todo-app/worktrees";
+
+    // ServicePage
+    public int SignalRPort { get; set; } = 47_821;
+    public int QueueBackstopIntervalMs { get; set; } = 30_000;
+    public string ClaudeBin { get; set; } = "claude";
+    public string ServiceAccount { get; set; } = "LocalSystem";
+    public bool AutoStart { get; set; } = true;
+    public int RestartDelayMs { get; set; } = 5000;
+
+    // UiSettingsPage
+    public string SignalRUrl { get; set; } = "http://127.0.0.1:47821/hub";
+    public string UiDbPath { get; set; } = "~/.todo-app/todo.db";
+
+    // InstallPage
+    public bool CreateDesktopShortcut { get; set; } = true;
+}