Fix HTTP 204 status code response handling

- Modified delete_user_endpoint to return None for HTTP 204 status code
- Updated delete_todo endpoint to also return None for HTTP 204 status code
- Added proper return type annotations to both endpoints
- This fixes the AssertionError: Status code 204 must not have a response body

app/api/todos.py

@@ -78,10 +78,12 @@ def delete_todo(
     todo_id: int, 
     db: Session = Depends(get_db),
     current_user: User = Depends(get_current_active_user)
-):
+) -> None:
     """
     Delete a todo item for the current user.
     """
     success = todo_crud.delete_todo(db, todo_id=todo_id, owner_id=current_user.id)
     if not success:
         raise HTTPException(status_code=404, detail="Todo not found")
+    # Explicitly return None for 204 response
+    return None

app/api/users.py

@@ -74,7 +74,7 @@ def delete_user_endpoint(
     user_id: int,
     db: Session = Depends(get_db),
     current_user: User = Depends(get_current_active_user),
-):
+) -> None:
     """
     Delete a user.
     """
@@ -88,3 +88,5 @@ def delete_user_endpoint(
     success = delete_user(db, user_id=user_id)
     if not success:
         raise HTTPException(status_code=404, detail="User not found")
+    # Explicitly return None for 204 response
+    return None