style(ActivityDetailPage): 将底部价格容器的对齐方式从 items-end 改为 items-center

将底部价格容器的对齐方式从 items-end 改为 items-center，以改善视觉一致性和布局美观性。

@@ -419,7 +419,7 @@ const RightContent = defineComponent({
       <div
         class="fixed bottom-16 left-0 right-0 bg-white p-3 shadow-lg flex justify-between items-center"
       >
-        <div class="flex items-end">
+        <div class="flex items-center">
           <div class="text-red-500 text-lg font-bold">¥366</div>
           <div class="text-xs text-gray-500 ml-1 line-through">原价¥468</div>
         </div>