feat(core,react): create user passkey hook

[NaveenChand755]

Summary

New hook that owns all passkey management UI state and action handlers for the UserPasskeyMgmt component.

Why

1. Keeps UI logic separate from data/cache logic

What

1. Orchestrates passkey UI state and action handlers on top of useUserPasskeyService
2. ActiveModal union drives modal open state and current passkey from one variable
3. onBefore/onAfter hooks per action, readOnly derived flag, onErrorAction notification

Packages

• packages/core
• packages/react
• examples

References

Testing

How can this be verified? Note anything intentionally not covered by tests and why.

• This change adds unit test coverage
• Tested for both SPA and RWA flows, all example apps working
• All existing and new tests complete without errors

Checklist

• Breaking change
• Requires docs update
• Backward compatible

Contributing

• I have read the Auth0 general contribution guidelines
• I have read the Auth0 Code of Conduct