fix(config): enable overriding of environment variables when loading .env file

backend/app/config.py

@@ -11,10 +11,10 @@ from dotenv import load_dotenv
 project_root_env = os.path.join(os.path.dirname(__file__), '../../.env')
 
 if os.path.exists(project_root_env):
-    load_dotenv(project_root_env)
+    load_dotenv(project_root_env, override=True)
 else:
     # 如果根目录没有 .env，尝试加载环境变量（用于生产环境）
-    load_dotenv()
+    load_dotenv(override=True)
 
 
 class Config: