A restart-safe cron worker runs outside the gateway, queues its final send in
cron/deliveries.db and polls that row once a second. The gateway drained the
queue only as a housekeeping chore at the 60 s tick, so a reminder whose turn
ended in 8 s reached the user a minute later (the issue's 60.86 s silence).
The housekeeping thread now watches the queue file (and its WAL) between
ticks and drains as soon as a stamp moved; the tick's drain stays as the
fallback. The watch never resets itself after draining: the drain's own status
write costs one empty pass, a worker that enqueued during the drain still
wakes it, and an empty pass writes nothing, so the stamp settles.
Fixes#117307
