⚡️ perf: Defer Visactor chart libs to dashboard; minimize home bundle

Home started loading `/assets/visactor-*.js` due to static imports of `@visactor/react-vchart` and the Semi theme in dashboard components/hooks. This change moves chart dependencies to lazy/dynamic imports so they load only on dashboard routes.

Changes
- StatsCards.jsx: replace static `VChart` import with `React.lazy` + `Suspense` (fallback: null)
- ChartsPanel.jsx: replace static `VChart` import with `React.lazy` + `Suspense` (fallback: null)
- useDashboardCharts.js: remove static `initVChartSemiTheme` import; dynamically import and initialize the theme inside `useEffect` with a cancel guard

Behavior
- Home page no longer downloads `visactor` chunks on first load
- Chart libraries are fetched only when visiting `/console` (dashboard)
- No functional changes to chart rendering

Files
- web/src/components/dashboard/StatsCards.jsx
- web/src/components/dashboard/ChartsPanel.jsx
- web/src/hooks/dashboard/useDashboardCharts.js

Verification
- Build the app (`npm run build`) and open `/`: no `/assets/visactor-*.js` requests
- Navigate to `/console`: `visactor` chunks load and charts render as expected

Breaking Changes
- None

Follow-ups
- If needed, further trim homepage bundle by reducing heavy icon sets on the hero section

web/src/hooks/dashboard/useDashboardCharts.js

@@ -18,7 +18,6 @@ For commercial licensing, please contact support@quantumnous.com
 */
 
 import { useState, useCallback, useEffect } from 'react';
-import { initVChartSemiTheme } from '@visactor/vchart-semi-theme';
 import {
   modelColorMap,
   renderNumber,
@@ -418,9 +417,19 @@ export const useDashboardCharts = (
 
   // ========== 初始化图表主题 ==========
   useEffect(() => {
-    initVChartSemiTheme({
-      isWatchingThemeSwitch: true,
-    });
+    // 动态加载 visactor 主题，避免首页首屏加载
+    let canceled = false;
+    (async () => {
+      try {
+        const mod = await import('@visactor/vchart-semi-theme');
+        if (!canceled && mod?.initVChartSemiTheme) {
+          mod.initVChartSemiTheme({ isWatchingThemeSwitch: true });
+        }
+      } catch (e) {
+        // 忽略加载失败，图表页再尝试
+      }
+    })();
+    return () => { canceled = true; };
   }, []);
 
   return {