feat: 添加完整的前端管理系统 (VbenAdmin)

- 添加基于 VbenAdmin + Vue3 + Element Plus 的前端管理系统
- 包含完整的 UI 组件库和工具链
- 支持多应用架构 (web-ele, backend-mock, playground)
- 包含完整的开发规范和配置
- 修复 admin 目录的子模块问题，确保正确提交

admin/apps/backend-mock/api/system/menu/name-exists.ts

@@ -0,0 +1,29 @@
+import { eventHandler, getQuery } from 'h3';
+import { verifyAccessToken } from '~/utils/jwt-utils';
+import { MOCK_MENU_LIST } from '~/utils/mock-data';
+import { unAuthorizedResponse, useResponseSuccess } from '~/utils/response';
+
+const namesMap: Record<string, any> = {};
+
+function getNames(menus: any[]) {
+  menus.forEach((menu) => {
+    namesMap[menu.name] = String(menu.id);
+    if (menu.children) {
+      getNames(menu.children);
+    }
+  });
+}
+getNames(MOCK_MENU_LIST);
+
+export default eventHandler(async (event) => {
+  const userinfo = verifyAccessToken(event);
+  if (!userinfo) {
+    return unAuthorizedResponse(event);
+  }
+  const { id, name } = getQuery(event);
+
+  return (name as string) in namesMap &&
+    (!id || namesMap[name as string] !== String(id))
+    ? useResponseSuccess(true)
+    : useResponseSuccess(false);
+});