Replace the passkey creation form with a Codex dialog that explains what passkeys are and contains a simple "Add" button, without a name input.
(@KieranMcCann-WMF is still refining the design and language)
- When the "Add a passkey" button is clicked, open a Codex dialog instead of navigating to WebAuthnAddKeyForm
- When the user clicks the "Add" button, create their passkey
- To enable this, create an action API endpoint for creating a passkey
- Automatically generate a name for the passkey (this can be something simple until T410938 is done)
