fix: 修复小程序时间选择器显示问题

- detail.vue: 时间选择器使用条件编译，H5/APP用u-datetime-picker，小程序用原生picker
- 避免u-datetime-picker在小程序中默认显示

pages/detail/detail.vue

@@ -321,10 +321,10 @@
           
           <view class="form-item">
             <text class="form-label">交易时间</text>
+            <!-- #ifdef H5 || APP-PLUS -->
             <u-datetime-picker
               v-model="transactionForm.dateTimestamp"
               mode="date"
-              :show="true"
               @confirm="onDateChange"
             >
               <view class="form-select">
@@ -332,6 +332,19 @@
                 <u-icon name="arrow-down" size="14" color="#9CA3AF"></u-icon>
               </view>
             </u-datetime-picker>
+            <!-- #endif -->
+            <!-- #ifdef MP-WEIXIN -->
+            <picker mode="date" :value="transactionForm.transactionDate" @change="onDateChange">
+              <view class="form-select">
+                <text>{{ transactionForm.transactionDate || '请选择日期' }}</text>
+                <uni-icons type="bottom" size="14" color="#9CA3AF"></uni-icons>
+              </view>
+            </picker>
+            <!-- #endif -->
+                <text>{{ transactionForm.transactionDate || '请选择日期' }}</text>
+                <u-icon name="arrow-down" size="14" color="#9CA3AF"></u-icon>
+              </view>
+            </u-datetime-picker>
           </view>
           
           <view class="form-item">