Update frontend/src/App.css

frontend/src/App.css

@@ -68,6 +68,12 @@ th:hover {
   color: #2ecc71;
 }
 
+.sort-indicator {
+  display: inline-block;
+  margin-left: 4px;
+  transition: transform 0.2s ease;
+}
+
 td {
   padding: 12px;
   border-bottom: 1px solid #eee;