Fly Scheduled Machines Transactional Email with Rovela (2026): fly secrets + Idempotency-Key per Window
Run a Fly Scheduled Machine (hourly/daily/weekly/monthly) that starts then exits, load ROVELA_API_KEY from fly secrets, and POST /emails with Idempotency-Key scoped to the schedule window. Distinct from Render Cron, Railway cron, Vercel Cron routes, and GitHub Actions.