Demo passkey support

[Edamijueda]

PR for issue #45

[devondragon]

Hey @Edamijueda — thank you for this contribution! Your work on adding WebAuthn/Passkey support to the demo app was a great starting point and we really appreciate you taking the initiative on this.

We've been working on the WebAuthn support in parallel on the framework library side as well, and ended up building on your work with some additional changes:

• Upgraded to the stable 4.2.0 framework release with built-in WebAuthn support
• Replaced the JS prompt for renaming passkeys with a Bootstrap modal dialog
• Added security hardening (event delegation instead of global scope, user-friendly error messages, safe date parsing, JSON-first error response handling)
• Added production configuration with environment variable overrides
• Added passkey documentation to the README

Since the branch diverged significantly, we've opened #55 which includes your original commits with Co-authored-by credit. We're going to close this PR in favor of that one.

Thanks again for the contribution — it helped us move faster on getting passkey support into the demo app!

[devondragon]

Closing in favor of #55 which builds on this work. Thank you for the contribution!