Verified: no external URLs in frontend (no CDN fonts, no analytics,
no Google Fonts, no external scripts). All fonts use system fallback
chains (JetBrains Mono → Cascadia Code → Fira Code → monospace).
No outbound HTTP calls in backend code.
Added SecurityHeadersMiddleware enforcing:
- Content-Security-Policy: default-src 'self', script/font/connect
restricted to 'self', style allows 'unsafe-inline' for Vue scoped
styles, img allows data: URIs, object-src 'none', frame-ancestors
'none'
- X-Content-Type-Options: nosniff
- X-Frame-Options: DENY
- Referrer-Policy: no-referrer
These headers prevent any accidental introduction of external
resources in future development — CSP violations will block them.