- Add LLMEndpoint model to models.py with encrypted api_key field
- Create encryption.py with Fernet symmetric encryption (key derived from JWT_SECRET via PBKDF2)
- Implement full endpoints router: list, get, create, update, delete + test_connection
- Test endpoint calls adapter.test_connection() and list_models()
- API keys never exposed in responses; has_api_key boolean flag added
- 25 tests in test_endpoints.py, all 444 tests passing
