feat: dark/light mode + trading console BI + Chart.js local + fix themeScript

- Dark/light mode toggle across all pages (login, dashboard, corporate, admin, BI)
- BI Executive redesigned as permanent dark trading console (Bloomberg-style)
- Floating vertical nav with anchor scroll for mobile navigation
- Chart.js bundled locally (eliminates CDN dependency)
- Chart.js inlined in HTML for guaranteed loading
- Fix: themeScript </script> tag had literal backslash breaking HTML parser
- Fix: each chart wrapped in individual try/catch for graceful degradation
- No-cache headers on BI page to prevent stale HTML
- Robust init that handles DOMContentLoaded already fired

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/admin-home.js

@@ -2,7 +2,7 @@
  * Admin Home Dashboard - Fast daily overview
  * 3 flows: BRL→USD, USD→BRL, USD→USD (balance)
  */
-const { buildHeader, buildFooter, buildHead } = require('./ui-template');
+const { buildHeader, buildFooter, buildHead, getChartJsScript } = require('./ui-template');
 
 function buildAdminHomeHTML(stats, user) {
   const now = new Date().toLocaleString('pt-BR');
@@ -26,7 +26,7 @@ function buildAdminHomeHTML(stats, user) {
   const totalOntem = stats.brlUsd.ontem.qtd + stats.usdBrl.ontem.qtd + stats.usdUsd.ontem.qtd;
   const totalVar = calcVar(totalHoje, totalOntem);
 
-  const pageScripts = `<script src="https://cdn.jsdelivr.net/npm/chart.js@4.4.1/dist/chart.umd.min.js"></script>`;
+  const pageScripts = getChartJsScript();
 
   const pageCSS = `
   /* Trading Terminal - Live Rates */