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/router/modules/demo.ts

@@ -0,0 +1,11 @@
+import type { RouteRecordRaw } from 'vue-router'
+
+const M = {
+  demoIcons: 'menu.demoIcons',
+  demoList: 'menu.demoList',
+}
+
+export const demoRoutes: RouteRecordRaw[] = [
+  { path: 'demo/icons', name: 'DemoIcons', component: () => import('@/views/demo/Icons.vue'), meta: { i18n: M.demoIcons } },
+  { path: 'demo/list', name: 'DemoList', component: () => import('@/views/demo/list/Index.vue'), meta: { i18n: M.demoList } },
+]