VENUS-17 chore(db): emailOutbox terminal-row retention prune — sent/permanentlyFailed rows never deleted, accumulate unbounded (was factor in drain-outbox seq-scan slow-query). Add retention prune for sent/permanentlyFailed older than ~30d (evolutiva-commons retention hygiene; emailOutbox not audited → no setArchiveContext needed). Non-urgent: partial index on status IN ('pending','sending') already neutralizes perf impact; this caps table growth. Note: drain-outbox idle-gate + partial-index fix in flight separately.