Remove missing imports in init_app (#8)

Author: ColinToft

backend/python/app/models/__init__.py

@@ -80,6 +80,9 @@ def create_db_and_tables() -> None:
 def init_app(_app: Any | None = None) -> None:
     """Initialize database for the application"""
     # Import models to register them with SQLModel
+    from .entity import Entity  # noqa: F401
+    from .simple_entity import SimpleEntity  # noqa: F401
+    from .user import User  # noqa: F401
 
     init_database()