LG-9860: Fix platform authenticator reauthentication redirect

[aduth]

🎫 Ticket

LG-9860

🛠 Summary of changes

Fixes an issue where a user who is prompted for reauthentication after submitting platform authenticator setup will be returned to the Security Key setup screen after reauthentication. With these changes, they'll be correctly redirected back to the Face and Touch Unlock setup screen.

📜 Testing Plan

Recommend setting a very low reauthentication window in config/application.yml to facilitate testing:

reauthn_window: 20

1. Go to http://localhost:3000/
2. Sign in to an existing account or create an account and then sign in
3. Click "Add Face or Touch Unlock"
4. On the "Use your device" screen, wait 2 minutes, or the amount of seconds for reauthn_window if configured
5. Enter a nickname
6. Click "Continue" and complete the browser prompts
7. At this point, you should be prompted for MFA "reauthentication"
8. Complete the reauthentication

Before: You are redirected to set up Security Key after reauthentication
After: You are redirected to set up Face or Touch Unlock after reauthentication

[zachmargolis]

LGTM

[jmdembe]

Everything LGTM