When the panel runs on a domain+HTTPS and the user has a registered key, the 2FA
challenge offers "Mit Security-Key anmelden" alongside the TOTP/backup-code field.
A verified assertion completes login exactly like a TOTP success; rate-limit +
session gate reused. TOTP and backup codes remain fully usable.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>