chore: 初始化前端仓库并迁移 admin-ui

- 创建 rui-frontend 前端仓库
- 迁移 admin-ui 管理后台
- 创建 cashier-mobile 和 customer-mobile 占位项目
- 配置 pnpm workspace

admin-ui/src/service/user/index.ts

@@ -0,0 +1,6 @@
+export { userService } from './userService'
+export { userDetailService } from './userDetailService'
+export { userDeptService } from './userDeptService'
+export { userPostService } from './userPostService'
+export { levelService } from './levelService'
+export { levelLogService } from './levelLogService'