feat: 搭建应用基础框架

包含应用入口、根组件、路由配置（含登录守卫）、主布局、全局样式、ECharts 插件、类型定义、常量映射表及静态资源。

frontend/src/plugins/echarts.ts

@@ -0,0 +1,24 @@
+/**
+ * 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
+ */
+import { use } from 'echarts/core'
+import { CanvasRenderer } from 'echarts/renderers'
+import { LineChart } from 'echarts/charts'
+import {
+  GridComponent,
+  TooltipComponent,
+  LegendComponent,
+  DataZoomComponent,
+  MarkLineComponent,
+} from 'echarts/components'
+
+use([
+  CanvasRenderer,
+  LineChart,
+  GridComponent,
+  TooltipComponent,
+  LegendComponent,
+  DataZoomComponent,
+  MarkLineComponent,
+])