Fix #1: remove expiry_date from gift card INSERTs (rolling 24-month via last_used_at only) Fix #2: add FOR UPDATE to RedeemGiftCard SELECT (race condition) Fix #6: add ?type=customer|inventory filter to GetGiftCards Fix #7: add admin_audit_log INSERT to GetUserGiftCardBalanceAdmin Fix #10: refactor normalizeCode to validators.NormalizeGiftCardCode Schema: add admin_audit_log table (GDPR Article 30), update testdb.go Tests: expiry-date-null, inventory-filter, audit-log, db table references Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent) Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>