feat: 购物车左侧添加返回首页按钮

- topMenu.js: 添加 home-btn 圆形按钮 (el-icon-s-home)
- topMenu.js: 添加 goIndex() 方法跳转 /index
- dark-override.css: home-btn 图标样式(18px/灰色/hover蓝)

clientarea/hgcloud/css/dark-override.css

@@ -150,11 +150,21 @@ html, body {
 }
 
 .header-right .header-right-item {
-  display: flex !important;
-  align-items: center !important;
+  display: flex;
+  align-items: center;
 }
 
 /* ============ 顶栏右侧按钮 — 纯圆形 ============ */
+/* 首页按钮 */
+.home-btn i {
+  font-size: 18px !important;
+  color: #4E5969 !important;
+}
+
+.home-btn:hover i {
+  color: #165DFF !important;
+}
+
 /* 购物车按钮 */
 .header-right .header-right-item .right-item {
   width: 36px !important;