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/api.ts

@@ -3,7 +3,7 @@ import router from './router';
 import { clearStaffSession, reconcileStaffSessionFromToken, useAuthStore } from './stores/auth';
 import { ensureStaffSession, resetStaffSessionHydration } from './utils/session-hydrate';
 
-const api = axios.create({ baseURL: '/admin/api' });
+const api = axios.create({ baseURL: '/api' });
 
 let handling401 = false;
 let handling403Portal = false;