style(common): add grid layout for product panel in navigation

public/themes/dist_static/static/css/common.css

@@ -1524,8 +1524,12 @@ body {
   flex: 1;
   min-width: 0;
   display: flex;
-  /* grid-template-columns: repeat(4, minmax(0, 1fr)); */
   gap: 5rem 2rem;
+}
+/* 仅产品下第一个面板用 4 列 grid */
+.nav-mega__dropdown-content.product .nav-mega__panel:first-child .nav-mega__cols {
+  display: grid;
+  grid-template-columns: repeat(4, minmax(0, 1fr));
 }.nav-mega__cols--solution {
   flex: none;
   grid-template-columns: repeat(7, max-content);