fix: use localhost for BaoDan admin URL in local dev

Replace hardcoded server IP 150.5.135.143 with localhost in
openDifyAdmin() to match local development environment.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend/src/App.vue

@@ -322,7 +322,7 @@ onMounted(() => {
 
 function openDifyAdmin() {
   // Dify 管理后台运行在 3000 端口
-  window.open('http://150.5.135.143:3000', '_blank')
+  window.open('http://localhost:3000', '_blank')
   showMobileMenu.value = false
 }