Update static/index.css

static/index.css

@@ -54,6 +54,10 @@ button-group {
       justify-content: center;
       gap: 8px;
     }
+      @keyframes spin {
+      0% { transform: rotate(0deg); }
+      100% { transform: rotate(360deg); }
+    }
 .btn-primary {
       background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
       color: white;