fix: add expire_on_commit=False to sessionmaker

Co-authored-by: aider (openrouter/thinkingmachines/inkling-small:free) <aider@aider.chat>

backend/app.py

@@ -7,7 +7,7 @@ import os
 
 DATABASE_URL = "sqlite:///./backend/golf.db"
 engine = create_engine(DATABASE_URL, connect_args={"check_same_thread": False})
-SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine, expire_on_commit=False)
 Base = declarative_base()
 
 class User(Base):