feat(stack): 新增 stack 模式管理功能

- 新增 `php think admin:stack:mode` 命令，支持 list/use/current/rollback 操作
- 新增 StackModeService 服务，负责模式切换、备份与回滚逻辑
- 在 source/stack/ 目录下添加 default、full、base-build 三种模式的配置文件
- 更新 UlthonAdminService 以注册新的命令行工具

extend/think/UlthonAdminService.php

@@ -25,6 +25,7 @@ use app\common\command\admin\role\AdminRoleList;
 use app\common\command\admin\role\AdminRolePermissionAssign;
 use app\common\command\admin\role\AdminRolePermissionList;
 use app\common\command\admin\role\AdminRolePermissionRevoke;
+use app\common\command\admin\stack\AdminStackMode;
 use app\common\command\admin\user\AdminUserRoleAssign;
 use app\common\command\admin\user\AdminUserRoleList;
 use app\common\command\admin\user\AdminUserRoleRevoke;
@@ -114,6 +115,7 @@ class UlthonAdminService extends Service
             AdminRolePermissionAssign::class,
             AdminRolePermissionRevoke::class,
             AdminRolePermissionList::class,
+            AdminStackMode::class,
             AdminUserRoleAssign::class,
             AdminUserRoleRevoke::class,
             AdminUserRoleList::class,