Surface the admin_audit table (written by every mutating admin action but
previously unreadable) as a new /admin/audit tab. New repo::admin_audit::list
(LEFT JOIN users for the actor's username, filter by action/target_kind/actor/
since, at DESC via admin_audit_at_idx) behind GET /v1/admin/audit, mirroring the
crawler history endpoint's paged/clamped idiom.
Frontend: a self-contained AuditTable (target-kind + window + action filters,
expandable JSON payload, AbortController-cancelled fetches, loading/error/empty
states) and shared fmtAgo() in format.ts.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
