[Feature request] Support custom user-agent when subscribe/订阅界面支持自定义user-agent

[gwd0715]

Please add a new feature that supports customized user-agent when subscribe, because some of the service suppliers only support mobile type user-agent to make a request. 能否支持自定义user-agent呢？机场节点订阅有防火墙，只支持手机类型的user-agent请求，才会有节点信息返回。

[1715173329]

应该去找你的机场，而不是本项目。