LG-10233: Sign in "Use face or touch unlock" page revisions

[aduth]

🎫 Ticket

LG-10233

🛠 Summary of changes

Updates content and experience for Face or Touch Unlock (and Security Key) authentication during sign-in:

• Green lock screen goes away, redirects immediately
• "Remember browser" button shown before authentication
• New content below spinner ("Authenticating your credentials…")
• Troubleshooting module on use f/t unlock sign in flow

📜 Testing Plan

1. Sign in with an account that has Security Key or Face or Touch Unlock configured
2. Observe updated verification page in sign-in

👀 Screenshots

Authenticator	Before	After
Security Key
Face or Touch Unlock

[aduth]

Marking this ready to review.

Regarding original draft comments:

Blocked by availability of new help center content

To unblock, I removed the help center link in 02c631d. We'll want to add it back when the help center content is published (tracked in LG-10200). If that's complete before end-of-sprint, I'll do a follow-on pull request, otherwise track as a new ticket.

Will plan to split out refactor for improved testability of webauthn verification behavior (i.e. submit after complete)

This is drafted at #8753, but I'll plan to finish that as a follow-on rather than splitting out.