fix(ui): Element Plus 启用中文语言包(zh-cn)

引入 element-plus/es/locale/lang/zh-cn，使组件(日期/分页/弹窗等)显示中文。

vue-app/src/main.js

 import { createApp } from 'vue'
 import { createPinia } from 'pinia'
 import ElementPlus from 'element-plus'
+import zhCn from 'element-plus/es/locale/lang/zh-cn'
 import 'element-plus/dist/index.css'
 import * as ElementPlusIconsVue from '@element-plus/icons-vue'
 
@@ -16,6 +17,6 @@ for (const [key, component] of Object.entries(ElementPlusIconsVue)) {
 
 app.use(createPinia())
 app.use(router)
-app.use(ElementPlus)
+app.use(ElementPlus, { locale: zhCn })
 
 app.mount('#app')