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/element-plus/theme-chalk/src/skeleton.scss

@@ -0,0 +1,44 @@
+@use 'mixins/mixins' as *;
+@use 'mixins/var' as *;
+@use 'common/var' as *;
+
+@include b(skeleton) {
+  @include set-component-css-var('skeleton', $skeleton);
+}
+
+@mixin skeleton-color() {
+  background: linear-gradient(
+    90deg,
+    getCssVar('skeleton-color') 25%,
+    getCssVar('skeleton-to-color') 37%,
+    getCssVar('skeleton-color') 63%
+  );
+  background-size: 400% 100%;
+  animation: #{$namespace}-skeleton-loading 1.4s ease infinite;
+}
+
+@keyframes #{$namespace}-skeleton-loading {
+  0% {
+    background-position: 100% 50%;
+  }
+  100% {
+    background-position: 0 50%;
+  }
+}
+
+@include b(skeleton) {
+  width: 100%;
+  @each $unit in (first-line, paragraph) {
+    @include e($unit) {
+      height: 16px;
+      margin-top: 16px;
+      background: getCssVar('skeleton-color');
+    }
+  }
+
+  @include when(animated) {
+    .#{$namespace}-skeleton__item {
+      @include skeleton-color();
+    }
+  }
+}