Frontend additions for add passkey flow

What does this MR do and why?

This is the Frontend only portion for the add passkey flow, separated out from the larger POC MR. It is behind a feature flag.

Passkeys Creation Flow (!209868) • Fernando Cardenas • 18.6

References

Screenshots or screen recordings

Before	After

How to set up and validate locally

Note: You cannot verify in this MR since the backend MR is missing. To test locally, checkout the integration MR Passkeys Creation Flow (!209868) • Fernando Cardenas • 18.6

This MR is only good for a code review and passing pipeline/unit tests.

• Navigate to the 2FA page
• Click Add Passkey
• Add Passkey

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Related to #437809