Record the very first device a user is ever seen on silently. The
new-device sign-in alert only carries meaning once there is an
established device to contrast against, so an empty device ledger
establishes the baseline without firing a notification; alerts begin
with the second distinct device. Registration's silent first-device
behaviour is unchanged.
Also extend the destructive-action step-up to treat a registered
security key as an active second factor, matching requireFreshMfa, so a
key-only account cannot delete or reset without a fresh factor.
Marc-André Bombeck
45a49f3d6d