Fix webauthn_utils MIME type error by adding importmap pin (#458)

The webauthn_utils module was not pinned in the importmap, so the
browser tried to fetch it as a regular HTTP request which returned
HTML instead of JavaScript. Pin it and change the imports from
relative paths to the pinned module name.

https://claude.ai/code/session_017U5qBWgHBppLwz5kp9Vbhp

Co-authored-by: Claude <noreply@anthropic.com>

Author: stefan-burke

app/javascript/passkey_login.js

@@ -3,7 +3,7 @@ import {
   base64ToArrayBuffer,
   arrayBufferToBase64,
   postJson,
-} from "./webauthn_utils";
+} from "webauthn_utils";
 
 document.addEventListener("turbo:load", () => {
   const loginButtons = document.querySelectorAll(

app/javascript/passkey_registration.js

@@ -3,7 +3,7 @@ import {
   base64ToArrayBuffer,
   arrayBufferToBase64,
   postJson,
-} from "./webauthn_utils";
+} from "webauthn_utils";
 
 window.registerPasskey = async function () {
   const nickname = prompt("Enter a nickname for this passkey:");

config/importmap.rb

@@ -14,6 +14,7 @@
 pin "guides_slider"
 pin "search"
 pin "image_resize"
+pin "webauthn_utils"
 pin "passkey_registration"
 pin "passkey_login"
 pin "text_replacement_form"