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/@cesium/engine/Source/Scene/BillboardLoadState.js

@@ -0,0 +1,44 @@
+/**
+ * Defines loading state of a image as any request is resolved and the WebGL resources are updated.
+ * @private
+ * @enum {number}
+ */
+const BillboardLoadState = Object.freeze({
+  /**
+   * There is no image data to load.
+   * @private
+   * @type {number}
+   * @constant
+   */
+  NONE: 0,
+  /**
+   * Image data is in the process of downloading, or WebGL resources are being updated.
+   * @private
+   * @type {number}
+   * @constant
+   */
+  LOADING: 2,
+  /**
+   * The image data has been downloaded and the WebGL resources have been created. It is ready for rendering.
+   * @private
+   * @type {number}
+   * @constant
+   */
+  LOADED: 3,
+  /**
+   * There was an error while downloading an image or updating the WebGL resources.
+   * @private
+   * @type {number}
+   * @constant
+   */
+  ERROR: 4,
+  /**
+   * Updating the WebGL resources failed, due to the resource being destroyed or another error.
+   * @private
+   * @type {number}
+   * @constant
+   */
+  FAILED: 5,
+});
+
+export default BillboardLoadState;