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/InstallerMode.cs

@@ -0,0 +1,19 @@
+using System.IO;
+using ClaudeDo.Data;
+
+namespace ClaudeDo.Installer.Core;
+
+public enum InstallerMode { Wizard, Settings }
+
+public static class ModeDetector
+{
+    public static InstallerMode Detect()
+    {
+        var root = Paths.AppDataRoot();
+        var workerConfig = Path.Combine(root, "worker.config.json");
+        var uiConfig = Path.Combine(root, "ui.config.json");
+        return File.Exists(workerConfig) && File.Exists(uiConfig)
+            ? InstallerMode.Settings
+            : InstallerMode.Wizard;
+    }
+}