feat: 帖子分级置顶（板块/全站）与板块管理员置顶权限、消息管理权限调整

backend/service/admin_user.go

@@ -470,7 +470,7 @@ func (s *AdminUserService) SetPermOverrides(operator *Actor, targetID uint, perm
 	return s.getItem(s.db, targetID)
 }
 
-// SetCanManageMessages 站长授予/撤销站点消息管理权限（不可操作站长账号与自己）
+// SetCanManageMessages 站长授予/撤销站点消息管理权限（超管亦需授予；不可操作站长账号与自己）
 func (s *AdminUserService) SetCanManageMessages(operator *Actor, targetID uint, enabled bool) (*AdminUserItem, error) {
 	if operator == nil || operator.Role != model.RoleOwner {
 		return nil, ErrOwnerOnly
@@ -486,10 +486,6 @@ func (s *AdminUserService) SetCanManageMessages(operator *Actor, targetID uint,
 		if u.Role == model.RoleOwner {
 			return ErrProtectedOwner
 		}
-		// 超管固有全站监管，flag 无意义；强制保持 false 以免误导
-		if u.Role == model.RoleSuperAdmin {
-			enabled = false
-		}
 		if u.CanManageMessages == enabled {
 			return nil
 		}