feat: implement user and forward max connection limit (#461)

* 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

go-backend/internal/store/repo/repository_flow.go

@@ -124,15 +124,16 @@ func (r *Repository) GetForwardRecord(forwardID int64) (*model.ForwardRecord, er
 		return nil, err
 	}
 	fr := model.ForwardRecord{
-		ID:         f.ID,
-		UserID:     f.UserID,
-		UserName:   f.UserName,
-		Name:       f.Name,
-		TunnelID:   f.TunnelID,
-		RemoteAddr: f.RemoteAddr,
-		Strategy:   f.Strategy,
-		Status:     f.Status,
-		SpeedID:    f.SpeedID,
+	        ID:         f.ID,
+	        UserID:     f.UserID,
+	        UserName:   f.UserName,
+	        Name:       f.Name,
+	        TunnelID:   f.TunnelID,
+	        RemoteAddr: f.RemoteAddr,
+	        Strategy:   f.Strategy,
+	        Status:     f.Status,
+	        SpeedID:    f.SpeedID,
+	        MaxConn:    f.MaxConn,
 	}
 	if strings.TrimSpace(fr.Strategy) == "" {
 		fr.Strategy = "fifo"