POST /checklist/send builds and emails a styled checklist from backlog AC items.
GET /checklist/:token verifies the HMAC signature, toggles the AC in the
markdown file, and re-renders the page with fresh links for remaining items.
Adds dev-ops volume mount and RTASKS_HMAC_SECRET/RTASKS_API_KEY env vars.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
