feat(tugboat): add preview environment with seeded demo data

Frank Mablyrequested to merge
issue/audit_trail-3591778:3591778-add-tugboat-preview into 1.x

drupal.org tugboat integration so MR reviewers and operators get a clickable preview of the admin surface without local install. Config + provisioning script seed a working chain (Key + audit_trail_secret + audit_trail_chain), emit ~30 chained entries spanning create / update / delete actions, archive the first segment, and surface admin/admin credentials in the build log.

Issue: #3591778

Closes #3591778

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