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>

src/auth/__init__.py

@@ -3,3 +3,25 @@ Authentication module for core-api
 
 Provides OIDC/OAuth2 authentication via Authentik
 """
+from src.auth.oidc import (
+    get_current_user,
+    get_admin_user,
+    get_optional_user,
+    get_forward_auth_user,
+    get_forward_auth_admin,
+    oidc_config,
+)
+from src.auth.service import AuthService, get_auth_service
+from src.auth.controller import auth_controller
+
+__all__ = [
+    "get_current_user",
+    "get_admin_user",
+    "get_optional_user",
+    "get_forward_auth_user",
+    "get_forward_auth_admin",
+    "oidc_config",
+    "AuthService",
+    "get_auth_service",
+    "auth_controller",
+]