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_preferences.py

@@ -0,0 +1,61 @@
+"""
+User Preferences Model
+
+Stores user-specific settings like theme and default room.
+"""
+import uuid
+
+from sqlalchemy import String, ForeignKey
+from sqlalchemy.dialects.postgresql import UUID, JSONB
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from src.db.database import Base
+
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from src.db.models.user import User
+
+
+class UserPreferences(Base):
+    """
+    User preferences model
+
+    Stores user-specific settings that persist across sessions.
+    Extended settings stored in preferences_json for flexibility.
+    """
+
+    __tablename__ = "user_preferences"
+
+    user_id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True),
+        ForeignKey("users.id", ondelete="CASCADE"),
+        primary_key=True,
+    )
+    theme: Mapped[str] = mapped_column(
+        String(20),
+        default="system",
+        nullable=False,
+        comment="Theme preference: system, light, dark",
+    )
+    default_room: Mapped[str] = mapped_column(
+        String(50),
+        default="front-hall",
+        nullable=False,
+        comment="Default room for housekeeping features",
+    )
+    preferences_json: Mapped[dict] = mapped_column(
+        JSONB,
+        default=dict,
+        nullable=False,
+        comment="Extended preferences as JSON",
+    )
+
+    # Relationships
+    user: Mapped["User"] = relationship(
+        "User",
+        back_populates="preferences",
+    )
+
+    def __repr__(self) -> str:
+        return f"<UserPreferences user_id={self.user_id}>"