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/model/model.go

@@ -23,6 +23,7 @@ type User struct {
 	CreatedTime   int64         `gorm:"column:created_time;not null"`
 	UpdatedTime   sql.NullInt64 `gorm:"column:updated_time"`
 	Status        int           `gorm:"not null"`
+	MaxConn       int           `gorm:"column:max_conn;not null;default:0"`
 }
 
 func (User) TableName() string { return "user" }
@@ -43,6 +44,7 @@ type Forward struct {
 	Status      int           `gorm:"not null"`
 	Inx         int           `gorm:"not null;default:0"`
 	SpeedID     sql.NullInt64 `gorm:"column:speed_id"`
+	MaxConn     int           `gorm:"column:max_conn;not null;default:0"`
 }
 
 func (Forward) TableName() string { return "forward" }
@@ -537,6 +539,7 @@ type ForwardRecord struct {
 	Strategy   string
 	Status     int
 	SpeedID    sql.NullInt64
+	MaxConn    int
 }
 
 // TunnelRecord is a minimal tunnel view used by control plane.