feat(web): 前端全局重构专业量化后台(深色+红涨绿跌+设计系统)

- 设计系统 styles/tokens.css: 深色token(#0d1117底/#161b22卡片) + 红涨绿跌
  (--up#f85149/--down#3fb950) + 品牌蓝#1890ff + 间距/圆角/阴影/mono
- Element Plus深色(element-dark.css + dark/css-vars)+reset
- 删Vite脚手架残留(style.css重写/HelloWorld/hero/vite/vue资源)
- Layout重构(深色专业侧边)+Login+图表统一深色(useChart/echartsDark)
- 新建paper/Live.vue实走监控(step状态/净值/持仓/今日信号10s轮询)
- 业务页套.page头, 保留所有功能/路由/api
- 验证: vue-tsc --noEmit ✅ + npm run build ✅

frontend/src/composables/useChart.ts

@@ -0,0 +1,28 @@
+/* ECharts 生命周期复用：init / setOption / resize / dispose 统一 */
+import { onMounted, onUnmounted, type Ref } from 'vue'
+import * as echarts from 'echarts'
+
+export function useChart(el: Ref<HTMLDivElement | undefined>) {
+  let chart: echarts.ECharts | null = null
+
+  function setOption(option: echarts.EChartsCoreOption): void {
+    chart?.setOption(option, true)
+  }
+
+  function resize(): void {
+    chart?.resize()
+  }
+
+  onMounted(() => {
+    if (el.value) chart = echarts.init(el.value)
+    window.addEventListener('resize', resize)
+  })
+
+  onUnmounted(() => {
+    window.removeEventListener('resize', resize)
+    chart?.dispose()
+    chart = null
+  })
+
+  return { setOption }
+}