[Due for payment 2026-03-31] [ECUK In-App 3DS] [App] Add usePasskeysBiometrics hook and WebAuthn helpers

[dariusz-biela]

Part of Adding biometric 3DS authentication for Expensify Cards

Implement part of this section of the design doc.

Add a usePasskeysBiometrics hook that handles Passkeys registration + authorization, manages frontend ↔ backend data exchange, and bridges low-level WebAuthn utils with MultifactorAuthenticationContext.

Additionally:

• Expose availability checks from the hook

  • Whether WebAuthn is supported in the current browser/device environment
  • Whether the user already has a passkey registered in this browser/device
    • Determine this by reconciling local Onyx passkeys with backend allowCredentials (see [ECUK In-App 3DS] [App] Add local passkeys storage utils in Onyx #79452)

• Add WebAuthn helpers

  • Normalize WebAuthn inputs/outputs into internal shapes
  • Provide ArrayBuffer ↔ base64url conversions
  • Normalize common WebAuthn errors into internal error shapes/codes

Issue Owner

Current Issue Owner: @dariusz-biela

[melvin-bot]

@dariusz-biela Whoops! This issue is 2 days overdue. Let's get this updated quick!

[dariusz-biela]

We plan to work on it, but the native biometrics issues need to be completed first.

[melvin-bot]

This issue has not been updated in over 14 days. @rafecolton, @dariusz-biela, @DylanDylann eroding to Weekly issue.