refactor(自定义标签栏): 使用计算属性替代ref获取购物车数量

将购物车数量从ref改为从store中获取的计算属性，保持数据同步性

components/custom-tab-bar/my-tab-bar.vue

@@ -1,10 +1,13 @@
 <script setup>
-import { ref } from "vue";
+import { computed, ref } from "vue";
+import useStore from "@/store";
 
 const props = defineProps({
   tabIndex: String | Number,
 });
 
+const store = useStore();
+
 /**
  * 底部导航栏下标
  */
@@ -20,7 +23,7 @@ const activeColor = "#06CA64";
 /**
  * 购物车数量
  */
-const cartCount = ref(0);
+const cartCount = computed(() => store.count);
 
 /**
  * 底部导航栏标签信息
@@ -93,6 +96,7 @@ function onChangeTab(index) {
       <view class="name" :style="{ color: activeTab === index ? activeColor : inactiveColor }">
         {{ tab.text }}
       </view>
+
       <view v-if="index === 3 && cartCount !== 0" class="badge">
         {{ cartCount }}
       </view>