feat(admin): migrate admin UI to Vue3

admin-frontend/src/main.js

@@ -0,0 +1,12 @@
+import { createApp } from 'vue'
+import App from './App.vue'
+
+import router from './router'
+
+import ElementPlus from 'element-plus'
+import zhCn from 'element-plus/es/locale/lang/zh-cn'
+import 'element-plus/dist/index.css'
+
+import './style.css'
+
+createApp(App).use(router).use(ElementPlus, { locale: zhCn }).mount('#app')