- Add withErrorAudit middleware tracking FORBIDDEN/UNAUTHORIZED/NOT_FOUND per user
- Fix impersonation attribution: log real admin ID, prefix IMPERSONATED_ on actions
- Add ACCOUNT_LOCKED audit events on login lockout (distinct from LOGIN_FAILED)
- Audit export of assignments and audit logs (meta-audit gap)
- Update audit page UI with new security event types and colors
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>