新增日志分隔符，优化chat_completion接口日志输出结构

app/api/routes.py

@@ -41,6 +41,7 @@ async def chat_completion(
     authorization: str = Header(None),
     token: str = Depends(security_service.verify_authorization),
 ):
+    logger.info("-" * 50)
     logger.info(f"Handling chat completion request for model: {request.model}")
     logger.info(f"Request: \n{request.model_dump_json(indent=2)}")
     api_key = await key_manager.get_next_working_key()