GDPR data export and configurable message retention

Administrators can now configure a retention window that auto-deletes conversations and messages after the set period. End users can download a ZIP archive of all their personal data — conversations, ratings, account metadata — directly from their account page, satisfying right-of-access and portability requests without an operator ticket. Messages are encrypted at rest using Fernet (AES-128-CBC).

No action required. Retention defaults to unlimited until an administrator configures a window.