Temporal Schedule Transactional Email with Rovela (2026): Calendar / Interval / Cron Spec + Activity Idempotency-Key
Wire Temporal Schedules (calendars, intervals, or cronExpressions) so a Workflow Activity calls Rovela POST /emails with server-only sending_access and a window-scoped Idempotency-Key. Distinct from BullMQ, Trigger.dev, Inngest, and QStash.