Fix Three.js import map (admin/viewer black canvas)

public/ar-head.html

@@ -78,6 +78,14 @@
   <script src="vendor/posit1.js"></script>
   <script src="vendor/aruco.js"></script>
   <script src="vendor/dictionaries/aruco_4x4_1000.js"></script>
+  <script type="importmap">
+  {
+    "imports": {
+      "three": "https://cdn.jsdelivr.net/npm/three@0.160.0/build/three.module.js",
+      "three/addons/": "https://cdn.jsdelivr.net/npm/three@0.160.0/examples/jsm/"
+    }
+  }
+  </script>
   <script type="module" src="js/ar-head.js"></script>
 </body>
 </html>