feat: 配置 CORS 以暴露上游响应时间标头

- 在 CORS 配置中添加 `x-one-api-upstream-time` 到 ExposeHeaders

middleware/cors.go

@@ -11,5 +11,6 @@ func CORS() gin.HandlerFunc {
 	config.AllowCredentials = true
 	config.AllowMethods = []string{"GET", "POST", "PUT", "DELETE", "OPTIONS"}
 	config.AllowHeaders = []string{"*"}
+	config.ExposeHeaders = []string{"x-one-api-upstream-time"}
 	return cors.New(config)
 }