🐛 fix(base.py): use db_manager.engine instead of DatabaseManager.engine to access the database engine

🐛 fix(conftest.py): add TYPE_CHECKING import to fix type hinting error
🐛 fix(conftest.py): pass db_manager to blank_session_getter fixture to fix session creation error

src/backend/langflow/services/database/base.py

@@ -70,7 +70,7 @@ class DatabaseManager(Service):
 @contextmanager
 def session_getter(db_manager: DatabaseManager):
     try:
-        session = Session(DatabaseManager.engine)
+        session = Session(db_manager.engine)
         yield session
     except Exception as e:
         print("Session rollback because of exception:", e)