feat: add authentication and user management with Authentik integration

- Add PostgreSQL database with async SQLAlchemy
- Add Alembic migrations for schema management
- Add User, Role, UserPreferences, ApiKey models
- Add auth endpoints: /auth/me, /auth/users, /auth/users/sync-from-authentik
- Add token validation via Authentik userinfo endpoint
- Add bulk user sync from Authentik admin API
- Add database health check to diagnostics

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

requirements.txt

@@ -1,12 +1,13 @@
 # FastAPI and ASGI server
-fastapi~=0.115.0
-uvicorn[standard]>=0.34.0  # Updated for google-adk compatibility
-pydantic>=2.11.1,<3.0.0  # Required for google-cloud-aiplatform[agent-engines]
+fastapi>=0.115.0
+starlette>=0.49.1  # CVE-2025-54121, CVE-2025-62727
+uvicorn[standard]>=0.34.0
+pydantic>=2.11.1,<3.0.0
 pydantic-settings>=2.10.1
 
 # HTTP client
-httpx>=0.28.0  # Required for google-adk
-python-socketio[asyncio_client]~=5.11.0
+httpx>=0.28.0
+python-socketio[asyncio_client]>=5.14.0  # CVE-2025-61765
 
 # Web scraping
 beautifulsoup4~=4.12.0
@@ -22,6 +23,11 @@ pytz~=2024.1
 dnspython~=2.7.0
 
 # Authentication & Security
-PyJWT[crypto]~=2.9.0
-python-jose[cryptography]~=3.3.0
-cryptography~=43.0.0
+PyJWT[crypto]>=2.9.0
+python-jose[cryptography]>=3.4.0  # CVE PYSEC-2024-232, PYSEC-2024-233
+cryptography>=44.0.1  # CVE-2024-12797
+
+# Database
+sqlalchemy[asyncio]~=2.0.0
+asyncpg>=0.30.0
+alembic~=1.13.0