refactor: 前端构建按需化与 Mock 懒加载

移除全量 Element Plus 与全局 VChart 注册，改为按需引入样式与组件内局部图表；Mock 适配器改为按 VITE_ENABLE_MOCK 环境变量懒加载，生产默认不拦截请求；ECharts 精简为看板所需图表，各视图与 stores 同步适配。

frontend/src/plugins/echarts.ts

@@ -1,26 +1,20 @@
 /**
- * ECharts 按需引入
- * 仅注册训练曲线所需的模块，避免引入全量包以减小体积
+ * 服务看板图表按需注册。
  */
 import { use } from 'echarts/core'
 import { CanvasRenderer } from 'echarts/renderers'
-import { BarChart, LineChart, PieChart } from 'echarts/charts'
+import { BarChart, PieChart } from 'echarts/charts'
 import {
   GridComponent,
   TooltipComponent,
   LegendComponent,
-  DataZoomComponent,
-  MarkLineComponent,
 } from 'echarts/components'
 
 use([
   CanvasRenderer,
   BarChart,
-  LineChart,
   PieChart,
   GridComponent,
   TooltipComponent,
   LegendComponent,
-  DataZoomComponent,
-  MarkLineComponent,
 ])