refactor: 移除冗余的 __tab_index__ 存储逻辑

haha-admin-mp/src/components/CustomTabBar.vue

@@ -74,7 +74,6 @@ const switchTab = (index: number) => {
   if (currentIndex.value === index) return;
 
   currentIndex.value = index;
-  uni.setStorageSync('__tab_index__', index);
   uni.switchTab({
     url: tabPages[index]
   });