fix: 挂载 Element Plus 中文语言包

构建产物此前走内置英文默认，分页器显示 20/page、删除确认框显示 OK。
显式注入 zh-cn 后统一为中文，并同步更新按英文按钮定位的回归用例。

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

frontend/src/main.js

 import { createApp } from 'vue/dist/vue.esm-bundler.js';
 import ElementPlus from 'element-plus';
+// Element Plus 默认语言是英文，分页器会显示 20/page、Go to 之类；这里显式挂中文包。
+import zhCn from 'element-plus/es/locale/lang/zh-cn';
 import 'element-plus/dist/index.css';
 import App from './App.js';
 import AppPagination from './components/AppPagination.js';
@@ -12,7 +14,7 @@ import './styles/auth-state.css';
  * 关联文件：frontend/index.html、frontend/src/App.js、frontend/src/router/index.js。
  * 关联逻辑（调用链/数据流）：index.html -> main.js -> createApp() -> router -> 静态参考页或重构占位页。
  */
-const application = createApp(App).use(router).use(ElementPlus);
+const application = createApp(App).use(router).use(ElementPlus, { locale: zhCn });
 // 分页器全局注册：四个列表页共用一套外观与空数据表现，避免各页模板再次分叉。
 application.component('AppPagination', AppPagination);
 await router.isReady();

frontend/tests/device-asset.spec.js

@@ -77,7 +77,7 @@ test('keeps a referenced device visible after protected delete response', async
   await page.route('**/api/device-assets**', async route=>{const request=route.request();const data=request.method()==='GET'?{records:[{id:8,deviceName:'protected-device',imageAttachment1Url:null,imageAttachment2Url:null,userPersonId:null,userPersonName:null,userUsageStatus:'\u4f7f\u7528\u4e2d',assetRelationStatus:'\u5df2\u5173\u8054',createTime:'',updateTime:''}],total:1,page:1,size:20}:null;const response=request.method()==='DELETE'?{code:400,message:'\u8bbe\u5907\u4ecd\u88ab\u624b\u673a\u53f7\u8d44\u4ea7\u5f15\u7528\uff0c\u4e0d\u80fd\u5220\u9664',data:null}:{code:200,message:'success',data};await route.fulfill({contentType:'application/json',body:JSON.stringify(response)});});
   await page.goto('/asset/#/device-assets');
   await page.locator('.el-table').getByRole('button',{name:'\u5220\u9664'}).click();
-  await page.getByRole('button',{name:'OK'}).click();
+  await page.getByRole('button',{name:'确定'}).click();
   await expect(page.getByText('\u8bbe\u5907\u4ecd\u88ab\u624b\u673a\u53f7\u8d44\u4ea7\u5f15\u7528\uff0c\u4e0d\u80fd\u5220\u9664')).toBeVisible();
   await expect(page.locator('.el-table').getByText('protected-device',{exact:true})).toBeVisible();
 });