Update search placeholder in approve index page from dynamic text to static '订单号' for clarity.

pages/approve/index.vue

 <template>
     <view class="approve-page">
         <view class="search-bar">
-            <u-search v-model="keyword" :placeholder="currentTab === 0 ? '客户名称' : '申请内容'" shape="round" :showAction="false" bgColor="#f5f7fa"></u-search>
+            <u-search v-model="keyword" placeholder="订单号" shape="round" :showAction="false" bgColor="#f5f7fa"></u-search>
         </view>
 
         <view class="tabs-wrap">