Audit Chain 1.5.0

Off-system evidence export: chain rows leave the writer's trust boundary as
versioned, data-minimized NDJSON — identifiers and hash-chain columns only —
over HTTPS or to a locked file, with per-destination advance-only checkpoints
and at-least-once delivery. Export refuses while the last scheduled
verification is failing, plain HTTP off-host is refused, delivery is bounded
by timeouts, and ingest URLs are logged and checkpointed with credentials
stripped. Run it with drush audit-chain:export or the cron leg.