Deadline reminder emails
One email when an applicable deadline lands 30, 7, or 0 days out. The cron checks every corporation daily, computes the deadlines that match the corp's filing profile, and sends a single bundled email per corp. Skips ones that don't apply (no payroll = no T4 reminder). Toggle and override email address sit in Settings → Company. Cron is idempotent so a retry on the same day never double-sends.

