Initial implementation of Claude desktop app (Tauri v2)

Standalone native desktop app wrapping claude.ai with:
- Direct webview navigation to claude.ai (not iframe)
- System tray with close-to-tray behavior
- Native notification bridge (JS overrides browser Notification API)
- Navigation filter allowing only Claude, Anthropic, and OAuth domains
- External links open in system browser
- Session persistence via WebKitGTK cookies/localStorage
- Builds .deb and AppImage bundles

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src-tauri/capabilities/default.json

@@ -0,0 +1,20 @@
+{
+  "$schema": "../gen/schemas/desktop-schema.json",
+  "identifier": "default",
+  "description": "Default permissions for the main window",
+  "windows": ["main"],
+  "permissions": [
+    "core:default",
+    "core:window:default",
+    "core:window:allow-close",
+    "core:window:allow-show",
+    "core:window:allow-hide",
+    "core:window:allow-set-focus",
+    "core:webview:default",
+    "opener:default",
+    "notification:default",
+    "notification:allow-is-permission-granted",
+    "notification:allow-request-permission",
+    "notification:allow-notify"
+  ]
+}