fix: add global Vue error handler with user-facing toast

web/frontend/src/main.ts

@@ -1,6 +1,6 @@
 import { createApp } from 'vue'
 import { createPinia } from 'pinia'
-import ElementPlus from 'element-plus'
+import ElementPlus, { ElMessage } from 'element-plus'
 import 'element-plus/dist/index.css'
 import zhCn from 'element-plus/dist/locale/zh-cn.mjs'
 import './styles/global.css'
@@ -10,6 +10,11 @@ import router from './router'
 
 const app = createApp(App)
 
+app.config.errorHandler = (err, _instance, info) => {
+  console.error('Vue error:', err, info)
+  ElMessage.error('操作失败，请稍后重试')
+}
+
 app.use(createPinia())
 app.use(router)
 app.use(ElementPlus, { locale: zhCn })