fix: Lint fixes of core, models and schemas

app/core/database.py

@@ -1,4 +1,4 @@
-from collections.abc import AsyncGenerator
+from collections.abc import AsyncGenerator, Callable
 
 from sqlalchemy.ext.asyncio import AsyncEngine, create_async_engine
 from sqlmodel import SQLModel
@@ -38,9 +38,9 @@ async def get_db() -> AsyncGenerator[AsyncSession, None]:
             await session.close()
 
 
-def get_session_factory():
+def get_session_factory() -> Callable[[], AsyncSession]:
     """Get a session factory function for services."""
-    def session_factory():
+    def session_factory() -> AsyncSession:
         return AsyncSession(engine)
     return session_factory