Stuck DNS outbox

DNS and webhooks share the outbox. Failures never roll back the lease.

1. Overview outbox lag, or SQL:

SELECT id, topic, attempts, status, last_error, next_attempt_at
FROM outbox WHERE status <> 'done' ORDER BY id LIMIT 50;

2. pending with a future next_attempt_at is backoff. Fix BIND/TSIG/AD/clock.
3. failed (8 attempts) is dead-letter. Fix the cause, then:

UPDATE outbox SET status='pending', attempts=0, next_attempt_at=now() WHERE id=…;

4. Do not delete rows that still need DNS.
5. Duplicate upserts are expected.

Worker must reach BIND or nsupdate -g. See AD DDNS and BIND TSIG.