feat: remove legacy frontend, root routing, compliance ZIP with Chromium PDF, chat markdown styling

- Legacy frontend removed: React SPA served at / (no /app/ prefix)
- Compliance report ZIP: Chromium headless --print-to-pdf (identical to browser) + CSV findings
- Server-side generation state: .compliance_generating marker survives page navigation
- RAG enriched: Description + Rationale + Remediation + Audit extracted from CIS vector chunks
- Chat markdown: syntax highlighting (Catppuccin), styled headings/lists/tables/blockquotes/code
- Default model auto-selected on Chat Agent load

frontend-react/vite.config.ts

@@ -3,7 +3,7 @@ import react from '@vitejs/plugin-react';
 import path from 'path';
 
 export default defineConfig({
-  base: '/app/',
+  base: '/',
   plugins: [react()],
   resolve: {
     alias: {