[PUI] Updates for AdminButton (#8434)

* [PUI] Updates for AdminButton

- Hide if django admin interface is disabled
- Use correct admin URL

* Adjust InfoView

* Add playwright tests

src/backend/InvenTree/InvenTree/api.py

@@ -236,6 +236,9 @@ class InfoView(AjaxView):
             'platform': InvenTree.version.inventreePlatform() if is_staff else None,
             'installer': InvenTree.version.inventreeInstaller() if is_staff else None,
             'target': InvenTree.version.inventreeTarget() if is_staff else None,
+            'django_admin': settings.INVENTREE_ADMIN_URL
+            if (is_staff and settings.INVENTREE_ADMIN_ENABLED)
+            else None,
         }
 
         return JsonResponse(data)