refactor: 将应用实例创建移至模块级别并优化主程序

将应用实例创建从主程序移至模块级别，避免重复创建实例
主程序现在直接使用模块级别的应用实例，简化了启动逻辑

router/main.py

@@ -76,10 +76,14 @@ def create_app(router_secret: Optional[str] = None) -> FastAPI:
     return app
 
 
+# Create top-level app instance for uvicorn
+from config import ROUTER_SECRET
+app = create_app(router_secret=ROUTER_SECRET)
+
+
 if __name__ == "__main__":
-    from config import PORT, ROUTER_SECRET
+    from config import PORT
     import uvicorn
-    app = create_app(router_secret=ROUTER_SECRET)
     uvicorn.run(
         "router.main:app",
         host="0.0.0.0",