feat: 添加深度复制功能，优化自动分类逻辑；更新周期账单视图以显示下次执行时间

Web/src/views/PeriodicRecord.vue

@@ -36,6 +36,7 @@
                 </template>
               </van-cell>
               <van-cell title="分类" :value="item.classify || '未分类'" />
+              <van-cell title="下次执行时间" :value="formatDateTime(item.nextExecuteTime) || '未设置'" />
               <van-cell title="状态">
                 <template #value>
                   <van-switch 
@@ -246,6 +247,7 @@ import {
 } from '@/api/transactionPeriodic'
 import PopupContainer from '@/components/PopupContainer.vue'
 import ClassifySelector from '@/components/ClassifySelector.vue'
+import dayjs from 'dayjs'
 
 const router = useRouter()
 const navTitle = ref('周期账单')
@@ -507,6 +509,12 @@ const toggleEnabled = async (id, enabled) => {
   }
 }
 
+const formatDateTime = (date) => {
+  if (!date) return ''
+
+  return dayjs(date).format('YYYY-MM-DD HH:mm:ss')
+}
+
 // 重置表单
 const resetForm = () => {
   form.id = null