fix: switch admin to subdomain mode and fix frozen-lockfile build

- Remove /admin path prefix (using admin.protdskj.top subdomain instead)
- Change pnpm install to --no-frozen-lockfile for lockfile compatibility
- Simplify admin Nginx config to standard SPA serving

🤖 Generated with [Qoder][https://qoder.com]

apps/admin/src/router/index.ts

@@ -3,7 +3,7 @@ import { useAuthStore } from '../stores/auth';
 import { ensureStaffSession } from '../utils/session-hydrate';
 
 const router = createRouter({
-  history: createWebHistory('/admin'),
+  history: createWebHistory(),
   routes: [
     { path: '/login', component: () => import('../views/Login.vue'), meta: { public: true } },
     {