- Add MFA enrollment UI in new Settings page with QR code and backup secret
- Add TOTP challenge step to login flow for enrolled users
- Check AAL after login and show TOTP input when aal2 required
- Add disable MFA option with TOTP re-verification
- Only show MFA options for email/password users (not OAuth)
- Add Settings link to user dropdown menu
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
