Update static/app.css

static/app.css

@@ -16,7 +16,19 @@ html, body {
   background-color: rgba(0, 150, 255, 0.1) !important;
   border: 2px dashed #1ec9f3 !important;
 }
-
+.loader {
+            display: inline-block;
+            border: 2px solid #f3f3f3;
+            border-top: 2px solid #3b82f6;
+            border-radius: 50%;
+            width: 16px;
+            height: 16px;
+            animation: spin 1s linear infinite;
+        }
+        @keyframes spin {
+            0% { transform: rotate(0deg); }
+            100% { transform: rotate(360deg); }
+        }
 header {
     flex: 0 0 17vh;
     display: flex;