* docs: add implementation plan for max conn limit
* feat: add CLimiters support for websocket reporter
* feat: add max_conn field to user and forward models
* feat: implement max conn limiter dispatching
* feat: add maxConn to user and forward CRUD API
* feat: add max conn UI to user management and forward rules
* fix: load MaxConn in get forward record and add e2e contract test for max conn limit