Alerting on absence, for every integration

An alert per integration that fires when it stops doing anything, which is the category nobody adds.

- alert: IntegrationSilent
  expr: |
    sum by (integration) (
      increase(integration_success_total[6h])
    ) == 0
  for: 1h

six integrations, six alerts, and each needs a window
that matches its cadence:

  the supplier dispatch  twice daily      → 18h
  the payment webhook    continuous       → 1h
  the accounting export  monthly          → not an
                         alert. a calendar entry.

Every alert we had was for a value being too high and none for a value not arriving, which is how an integration fails silently for eleven weeks. The monthly export is the case that shows the limit — an absence alert needs a window shorter than the interval, and some intervals are too long for an alert to be the right tool.