Add UserConnTracker to manage user connection cancellations across proxies

[ImMohammad20000]

there is an old bug that lead to a big issue in panels that leve connections open when users remove from inbounds via gRPC api the connection to that user dose not close in some cases so i implement a connection tracker that track all connections and close theme when users remove from the inbounds

an example of the issue is user limited to 1GB but becouse connections not closed it used 18GB

[RPRX]

#5401 连接追踪是会加的，不过怎么设计还要再考虑下

我看了下你的代码，为啥要 register unregister，每个 user 内存中自带一个 ctx 然后被 remove 时直接 cancel() 不就行了

应该不用考虑整个入站被移除？那个连端口都被释放了

[ImMohammad20000]

I considered that approach, but I wanted to ensure connections are tracked across all proxies without relying on each inbound’s internal context, especially since the removal comes via gRPC API and the user might be referenced from multiple places. Using a separate tracker makes it explicit and easier to debug. Happy to refactor if you think a simpler ctx-based approach inside each user struct.

[Fangliding]

这不就是个机场计费 helper

[RPRX]

等新的正式版发布后再讨论一下吧