Inform user when server can't be reached on login

src/screens/Login.vue

@@ -52,7 +52,9 @@ onMounted(async () => {
   /**
    * Fetch assets from the server
    */
-  assetStore.fetchAssets()
+  if (!await assetStore.fetchAssets()) {
+    notifications.addNotification({ message: 'Failed to fetch assets, the server may be offline or in maintenance. Please try again later.' })
+  }
 })
 
 async function loginFunc() {