fix(frontend): BUG-001慢API超时兜底+BUG-002清理views残留.bak (产品打磨批次1 2026-09-03)

- api/index.ts: axios网络层错误(超时ECONNABORTED/断连)3s节流ElMessage提示,页面不再静默加载失败
- views: 删除6个.bak历史备份(BudgetManagement/CMAKnowledge/DeviationDashboard/KPIList/MapCanvas/MapReview),均已git跟踪可回溯
- nginx缓存策略另改(不进git): /assets/ immutable长缓存+index.html etag条件请求

frontend/src/api/index.ts

@@ -1,10 +1,14 @@
 import axios from 'axios'
+import { ElMessage } from 'element-plus'
 
 const api = axios.create({
   baseURL: '/api/cma',
   timeout: 15000,
 })
 
+// 网络层错误提示节流标记（3 秒内只弹一次）
+let lastNetErrToast = 0
+
 api.interceptors.request.use((config) => {
   const token = localStorage.getItem('cma_token')
   if (token) config.headers.Authorization = `Bearer ${token}`
@@ -19,6 +23,13 @@ api.interceptors.response.use(
       localStorage.removeItem('cma_token')
       localStorage.removeItem('cma_user')
       window.location.href = '/login'
+    } else if (error.code === 'ECONNABORTED' || !error.response) {
+      // BUG-001 兜底(2026-09-03)：网络层失败(超时/断连)节流提示，避免并行请求重复弹窗
+      const now = Date.now()
+      if (now - lastNetErrToast > 3000) {
+        lastNetErrToast = now
+        ElMessage.warning(error.code === 'ECONNABORTED' ? '请求超时，请稍后重试' : '网络异常，请检查连接后重试')
+      }
     }
     return Promise.reject(error)
   }