Fix access control in Admin Index and Navbar components

resources/views/components/navbar.blade.php

@@ -142,7 +142,7 @@
 
                 </ul>
             </details>
-            @if (isCloud())
+            @if (isCloud() && isInstanceAdmin())
                 <li title="Admin">
                     <a class="hover:bg-transparent" href="/admin">
                         <svg class="text-pink-600 icon" viewBox="0 0 256 256" xmlns="http://www.w3.org/2000/svg">