chore(core/frontend): remove dead codex-era exact-* code (§6)

Removed unused codex/iframe-era modules (confirmed no live imports; public/exact/*.html design baselines kept):
- routes/exact-document.tsx, routes/exact-html.ts (~1.6MB generated), routes/exact-dashboard.tsx, routes/exact-pages/ (24 files)
- exact-pages.css + its main.tsx import; index.ts ExactDashboardApp re-export
App.tsx uses the real Dashboard; nothing referenced the removed cluster.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

core/frontend/src/routes/index.ts

@@ -1,7 +1,6 @@
 
 
 export { AuthScreen } from "./auth-screen";
-export { ExactDashboardApp } from "./exact-dashboard";
 export { Dashboard } from "./dashboard";
 export { ProductsPage, ProductCreateUploadPage, ProductDetailPage } from "./products";
 export { ProjectWizardPage, ProjectsPage } from "./projects";