✨ feat: add admin-only "remark" support for users

* backend
  - model: add `Remark` field (varchar 255, `json:"remark,omitempty"`); AutoMigrate handles schema change automatically
  - controller:
    * accept `remark` on user create/update endpoints
    * hide remark from regular users (`GetSelf`) by zero-ing the field before JSON marshalling
    * clarify inline comment explaining the omitempty behaviour

* frontend (React / Semi UI)
  - AddUser.js & EditUser.js: add “Remark” input for admins
  - UsersTable.js:
    * remove standalone “Remark” column
    * show remark as a truncated Tag next to username with Tooltip for full text
    * import Tooltip component
  - i18n: reuse existing translations where applicable

This commit enables administrators to label users with private notes while ensuring those notes are never exposed to the users themselves.

model/user.go

@@ -41,6 +41,7 @@ type User struct {
 	DeletedAt        gorm.DeletedAt `gorm:"index"`
 	LinuxDOId        string         `json:"linux_do_id" gorm:"column:linux_do_id;index"`
 	Setting          string         `json:"setting" gorm:"type:text;column:setting"`
+	Remark           string         `json:"remark,omitempty" gorm:"type:varchar(255)" validate:"max=255"`
 }
 
 func (user *User) ToBaseUser() *UserBase {
@@ -366,6 +367,7 @@ func (user *User) Edit(updatePassword bool) error {
 		"display_name": newUser.DisplayName,
 		"group":        newUser.Group,
 		"quota":        newUser.Quota,
+		"remark":       newUser.Remark,
 	}
 	if updatePassword {
 		updates["password"] = newUser.Password