style: 移除MyActivitiesPage.vue中的冗余样式并调整ActivityCard.vue的布局

移除MyActivitiesPage.vue中的`space-y-4`样式，以避免不必要的间距。同时，在ActivityCard.vue中添加`block mb-4`类，以确保卡片之间的间距一致。

 <!--
  * @Date: 2025-03-20 20:36:36
  * @LastEditors: hookehuyr hookehuyr@gmail.com
- * @LastEditTime: 2025-03-21 15:37:21
+ * @LastEditTime: 2025-03-21 17:21:45
  * @FilePath: /mlaj/src/components/ui/ActivityCard.vue
  * @Description: 文件描述
 -->
 <template>
-  <router-link :to="`/activities/${activity.id}`">
+  <router-link :to="`/activities/${activity.id}`" class="block mb-4">
     <FrostedGlass class="flex overflow-hidden rounded-xl shadow-sm">
       <!-- Activity Image -->
       <div class="w-1/3 h-28 relative">

 <!--
  * @Date: 2025-03-21 11:47:47
  * @LastEditors: hookehuyr hookehuyr@gmail.com
- * @LastEditTime: 2025-03-21 11:47:48
+ * @LastEditTime: 2025-03-21 17:21:32
  * @FilePath: /mlaj/src/views/activities/MyActivitiesPage.vue
  * @Description: 文件描述
 -->
@@ -13,7 +13,7 @@
       :finished="finished"
       finished-text="没有更多了"
       @load="onLoad"
-      class="px-4 py-3 space-y-4"
+      class="px-4 py-3"
     >
       <ActivityCard
         v-for="activity in activities"