error message

frontend/index.html

@@ -93,6 +93,11 @@
         </div>
     </div>
 
+    <div id="error-toast" class="error-toast" role="alert" aria-live="assertive">
+        <span id="error-toast-text"></span>
+        <button id="error-toast-close" type="button" aria-label="Close">✕</button>
+    </div>
+
     <script src="static/app.js"></script>
     <script src="https://cdn.jsdelivr.net/npm/hls.js@latest"></script>
 </body>