refactor(guest): retire legacy guest app and move shared modules

resources/js/shared/guest/lib/device.ts

@@ -0,0 +1,19 @@
+export function getDeviceId(): string {
+  const KEY = 'device-id';
+  let id = localStorage.getItem(KEY);
+  if (!id) {
+    id = genId();
+    localStorage.setItem(KEY, id);
+  }
+  return id;
+}
+
+function genId() {
+  // Simple UUID v4-ish generator
+  return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, (c) => {
+    const r = (crypto.getRandomValues(new Uint8Array(1))[0] & 0xf) >> 0;
+    const v = c === 'x' ? r : (r & 0x3) | 0x8;
+    return v.toString(16);
+  });
+}
+