Alert-engine liveness watchdog. 200 if the alert-evaluation loop AND Telegram deliverability are both fresh; 503 otherwise. Point a FREE UptimeRobot HTTP monitor here — if alerts silently stop delivering (as they did for 11 days in Aug 2026 with nobody noticing), this flips to 503 and UptimeRobot emails you within minutes.

Heartbeats (unix-ts in meta, written by routes_alerts): hb_alert_dispatch — the per-tx alert-evaluation path ran (stale >15min = stalled engine) hb_alert_canary — Telegram sendChatAction/getMe succeeded (stale >20min = delivery broken) hb_alert_delivery (last real user delivery) is reported for visibility only — it is legitimately sparse when few subscriptions match, so it is NEVER an alarm condition.