feat: 实现供水运营专题大屏BI可视化

- 新增OperationDashboard.vue全屏大屏组件
- 添加6个核心KPI指标卡片: 进水总量/出水总量/产销差率/营收额/平均水质/报警次数
- 实现6个ECharts图表: 供水趋势/水质分布/报警统计/管网空间/设备状态/营收分析
- 创建静态HTML版本operation-dashboard.html，使用CDN加载Vue3/ECharts/Element Plus
- 更新路由配置，添加/operation路径支持
- 修复nextTick导入问题，优化build脚本

🚧 开发者: bot_dev1
📝 任务: #38 [BI] 运营仪表盘 + 供水专题大屏

frontend/node_modules/axios/lib/helpers/throttle.js

@@ -0,0 +1,44 @@
+/**
+ * Throttle decorator
+ * @param {Function} fn
+ * @param {Number} freq
+ * @return {Function}
+ */
+function throttle(fn, freq) {
+  let timestamp = 0;
+  let threshold = 1000 / freq;
+  let lastArgs;
+  let timer;
+
+  const invoke = (args, now = Date.now()) => {
+    timestamp = now;
+    lastArgs = null;
+    if (timer) {
+      clearTimeout(timer);
+      timer = null;
+    }
+    fn(...args);
+  };
+
+  const throttled = (...args) => {
+    const now = Date.now();
+    const passed = now - timestamp;
+    if (passed >= threshold) {
+      invoke(args, now);
+    } else {
+      lastArgs = args;
+      if (!timer) {
+        timer = setTimeout(() => {
+          timer = null;
+          invoke(lastArgs);
+        }, threshold - passed);
+      }
+    }
+  };
+
+  const flush = () => lastArgs && invoke(lastArgs);
+
+  return [throttled, flush];
+}
+
+export default throttle;