url报错修复

backend/app/config.py

@@ -70,7 +70,8 @@ DB_NAME = _get_str("DB_NAME")
 
 # 完整连接字符串（直接从环境变量读取）
 DB_URI = _get_str("DB_URI")
-
+if not DB_URI and all([DB_HOST, DB_PORT, DB_USER, DB_PASSWORD, DB_NAME]):
+    DB_URI = f"postgresql://{DB_USER}:{DB_PASSWORD}@{DB_HOST}:{DB_PORT}/{DB_NAME}?sslmode=disable"
 
 # ========== 后端服务配置 ==========
 BACKEND_PORT = _get_int("BACKEND_PORT")