When LoadActiveAlerts skipped acknowledged alerts older than 1 hour,
it was also not populating ackState. This meant that when the same
alert (e.g., backup-age) was recreated on the next poll cycle,
preserveAlertState couldn't find any acknowledgement record and
the alert would retrigger notifications.
Now ackState is populated even for skipped old acknowledged alerts,
so if they reappear, the acknowledgement will be restored.
Related to #1043
48fdff3efb