- Add rate limiting (5 submissions per IP per 10 min, per share link)
to prevent abuse of shared submission endpoints
- Replace all plain die() error responses with styled flash messages
and redirects (invalid slug, disabled link, expired link, wrong password,
rate limit exceeded, CSRF failure)
- Add dedicated error page renderer for disabled/expired links with
home page link
- Password gate now uses flash message via session redirect instead
of inline error variable