Implement Password Grant Flow for Authentication and Enhance User Experience

- Introduced Password Grant Flow for user authentication, allowing direct login with email and password.
- Updated `useAuth` composable to manage login and logout processes, including Single Sign-Out from Cidaas.
- Enhanced user interface with a new `UserMenu` component displaying user information and logout functionality.
- Updated homepage to show personalized greetings for logged-in users and a login prompt for guests.
- Added logout confirmation page with a countdown redirect to the homepage.
- Documented the implementation details and future enhancements for OAuth2 flows in CLAUDE.md and other relevant documentation.
- Added test credentials and guidelines for automated testing in the new TESTING.md file.

server/api/test/credentials.get.ts

@@ -0,0 +1,18 @@
+/**
+ * GET /api/test/credentials
+ *
+ * Returns test user credentials for automated testing
+ *
+ * ⚠️ SECURITY: This endpoint is ONLY available in development mode.
+ * It returns 404 in production to prevent credential exposure.
+ *
+ * Usage in tests:
+ * ```typescript
+ * const response = await fetch('http://localhost:3000/api/test/credentials')
+ * const { email, password } = await response.json()
+ * ```
+ */
+
+import { createTestCredentialsEndpoint } from '../../utils/test-helpers'
+
+export default createTestCredentialsEndpoint()