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/utils/cookie-utils.ts

@@ -0,0 +1,28 @@
+import type { EventHandlerRequest, H3Event } from 'h3';
+
+import { deleteCookie, getCookie, setCookie } from 'h3';
+
+export function clearRefreshTokenCookie(event: H3Event<EventHandlerRequest>) {
+  deleteCookie(event, 'jwt', {
+    httpOnly: true,
+    sameSite: 'none',
+    secure: true,
+  });
+}
+
+export function setRefreshTokenCookie(
+  event: H3Event<EventHandlerRequest>,
+  refreshToken: string,
+) {
+  setCookie(event, 'jwt', refreshToken, {
+    httpOnly: true,
+    maxAge: 24 * 60 * 60, // unit: seconds
+    sameSite: 'none',
+    secure: true,
+  });
+}
+
+export function getRefreshTokenFromCookie(event: H3Event<EventHandlerRequest>) {
+  const refreshToken = getCookie(event, 'jwt');
+  return refreshToken;
+}