fix(admin): avoid locally caught exception in PasskeyLogin (#268)

* fix(admin): avoid locally caught exception in PasskeyLogin

Why:

The passkey login flow threw an error when navigator.credentials.get()
returned no credential, but that exception was immediately caught by the
local catch block in the same function. This triggered a
"throw of exception caught locally" warning and made the failure path
less direct.

What:

- Handle the missing credential case inline instead of throwing locally
- Preserve the existing error message shown to the user
- Keep the onError callback behavior unchanged

* Add changeset

---------

Co-authored-by: Matt Kane <m@mk.gg>
Co-authored-by: Matt Kane <mkane@cloudflare.com>

.changeset/serious-carrots-obey.md

@@ -0,0 +1,5 @@
+---
+"@emdash-cms/admin": patch
+---
+
+Fixes passkey login error handling when no credential is returned from the authenticator