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/db/models/user.py

@@ -0,0 +1,94 @@
+"""
+User Model
+
+Represents users synced from Authentik SSO.
+"""
+import uuid
+from datetime import datetime
+from typing import TYPE_CHECKING, List
+
+from sqlalchemy import String, Boolean, DateTime, func
+from sqlalchemy.dialects.postgresql import UUID
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from src.db.database import Base
+
+if TYPE_CHECKING:
+    from src.db.models.role import Role
+    from src.db.models.user_preferences import UserPreferences
+    from src.db.models.api_key import ApiKey
+
+
+class User(Base):
+    """
+    User model synced from Authentik
+
+    Users are created/updated when they authenticate via OIDC.
+    The authentik_id links to the Authentik user record.
+    """
+
+    __tablename__ = "users"
+
+    id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True),
+        primary_key=True,
+        default=uuid.uuid4,
+    )
+    authentik_id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True),
+        unique=True,
+        nullable=False,
+        index=True,
+    )
+    email: Mapped[str] = mapped_column(
+        String(255),
+        unique=True,
+        nullable=False,
+        index=True,
+    )
+    name: Mapped[str] = mapped_column(
+        String(255),
+        nullable=False,
+    )
+    avatar_url: Mapped[str | None] = mapped_column(
+        String(500),
+        nullable=True,
+    )
+    api_keys_enabled: Mapped[bool] = mapped_column(
+        Boolean,
+        default=True,
+        nullable=False,
+    )
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
+        server_default=func.now(),
+        nullable=False,
+    )
+    last_login: Mapped[datetime | None] = mapped_column(
+        DateTime(timezone=True),
+        nullable=True,
+    )
+
+    # Relationships
+    roles: Mapped[List["Role"]] = relationship(
+        "Role",
+        secondary="user_roles",
+        back_populates="users",
+        lazy="selectin",
+    )
+    preferences: Mapped["UserPreferences"] = relationship(
+        "UserPreferences",
+        back_populates="user",
+        uselist=False,
+        lazy="selectin",
+        cascade="all, delete-orphan",
+    )
+    api_keys: Mapped[List["ApiKey"]] = relationship(
+        "ApiKey",
+        back_populates="user",
+        lazy="selectin",
+        cascade="all, delete-orphan",
+    )
+
+    def __repr__(self) -> str:
+        return f"<User {self.email}>"