- Added new endpoint `/antigravity-auth-url` to initiate Antigravity authentication.
- Implemented `RequestAntigravityToken` to manage the OAuth flow, including token exchange and user info retrieval.
- Introduced `.oauth-antigravity` temporary file handling for state and code management.
- Added `sanitizeAntigravityFileName` utility for safe token file names based on user email.
- Registered `/antigravity/callback` endpoint for OAuth redirects.