Auto-suggest name for new Passkeys

- Use plain client data json everywhere
- Expose AAGUID and backed_up on Credentials
- Make attestation verifiers configurable
- Auto-suggest names for passkeys and show icons

db/migrate/20260219095815_add_aaguid_and_backed_up_to_identity_credentials.rb

@@ -0,0 +1,6 @@
+class AddAaguidAndBackedUpToIdentityCredentials < ActiveRecord::Migration[8.2]
+  def change
+    add_column :identity_credentials, :aaguid, :string
+    add_column :identity_credentials, :backed_up, :boolean
+  end
+end