fix: restore missing export to excel button and logic in blind stocktake page

inventory-web/src/views/stock/stocktake/index.vue

@@ -97,12 +97,17 @@
 
       <div class="main-actions">
         <el-row :gutter="10">
-          <el-col :span="12">
+          <el-col :span="8">
+            <el-button type="success" size="large" class="w-100 action-btn" @click="exportToExcel" :icon="Download">
+              导出Excel
+            </el-button>
+          </el-col>
+          <el-col :span="8">
             <el-button type="primary" plain size="large" class="w-100 action-btn" @click="openInventoryList" :icon="Search">
               盘点明细
             </el-button>
           </el-col>
-          <el-col :span="12">
+          <el-col :span="8">
             <el-button v-if="userStore.hasPermission('inventory_stocktake:operation')" type="danger" size="large" class="w-100 action-btn" @click="handleGenerateMissing" :icon="Checked">
               结束盘点并生成差异
             </el-button>