feat(06-02): add native desktop features — tray, window-state, autostart, version check

- Add GET /health/version public endpoint to API
- Extend Tauri with 4 plugins: notification, autostart, window-state, store
- Implement close-to-tray with prevent_close + prevent_exit (Pitfall 2)
- Tray menu with Oeffnen/Beenden (German labels)
- Async startup version check against server /health/version
- Generate Tessera-branded icons (yellow T on dark bg, OKLCH palette)
- Update capabilities for notification, autostart, window-state permissions

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

apps/api/src/health/health.controller.ts

@@ -12,4 +12,13 @@ export class HealthController {
       timestamp: new Date().toISOString(),
     };
   }
+
+  @Public()
+  @Get('version')
+  getVersion() {
+    return {
+      version: process.env.npm_package_version ?? '0.0.1',
+      name: 'tessera',
+    };
+  }
 }