client error messages

client/index.html

@@ -57,6 +57,11 @@
         </div>
       </div>
 
+      <div id="stage-error" class="stage d-none">
+          <h2 class="display-1">Error</h2>
+          <p class="lead">An error has occoured and the server has killed the connection. Refresh the page.</p>
+      </div>
+
       <!-- Staff Stage -->
       <div id="stage-staff" class="stage d-none">
 		<form class="row row-cols-lg-auto g-3 align-items-center" onsubmit="onStartAllocate(); return false;">