Update z-index value in Header component for improved layout

src/components/layout/Header.vue

@@ -41,7 +41,7 @@ export default {
 .app-header {
   position: sticky;
   top: 0;
-  z-index: 9999;
+  z-index: 1000;
   padding: 0 20px;
   display: flex;
   align-items: center;