feat: 商户订单/退款页面增加商户名称筛选功能

前端：
- 商户订单页面(index.vue)和退款页面(refund/index.vue)增加merchant-name组件
- 搜索表单新增"商户名称"下拉选择，支持远程搜索和分页加载
- 订单列表表格新增"商户名称"列(merName)
- 重置按钮同时清除商户筛选条件

后端：
- MerchantOrderPageResponse增加merId和merName字段
- OrderMapper.xml的getMerchantAdminPage查询JOIN eb_merchant表获取商户名称
- OrderServiceImpl: 平台管理员支持按request.merId筛选指定商户订单
- RefundOrderServiceImpl: 同样支持按request.merId筛选退款订单

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

mer_plat_admin/src/views/merchantOrder/refund/index.vue

@@ -58,6 +58,9 @@
               @keyup.enter.native="handleSearchList"
             />
           </el-form-item>
+          <el-form-item label="商户名称：">
+            <merchant-name @getMerId="getMerId" :merIdChecked="tableFrom.merId"></merchant-name>
+          </el-form-item>
           <el-form-item>
             <el-button type="primary" size="small" @click="handleSearchList">查询</el-button>
             <el-button size="small" @click="handleReset">重置</el-button>
@@ -282,6 +285,7 @@ import RefundOrderDetail from '../components/refundOrderDetail.vue';
 import { refundStatusFilter } from '@/filters';
 import useRefundOrder from '@/libs/useRefundOrder';
 import AgreeToReturn from '@/views/merchantOrder/components/agreeToReturn.vue';
+import merchantName from '@/components/merchantName';
 import * as $constants from '@/utils/constants';
 const { onConfirmReceipt, onApprovedReview } = useRefundOrder();
 const tableFroms = {
@@ -294,6 +298,7 @@ const tableFroms = {
   searchType: 'all',
   content: '',
   trackingNumber: '',
+  merId: null,
 };
 // 权限判断函数
 export default {
@@ -301,6 +306,7 @@ export default {
   components: {
     AgreeToReturn,
     RefundOrderDetail,
+    merchantName,
   },
   data() {
     return {
@@ -369,6 +375,10 @@ export default {
   },
   methods: {
     checkPermi,
+    getMerId(id) {
+      this.tableFrom.merId = id;
+      this.handleSearchList();
+    },
     //商家确认收货
     handleConfirmReceipt(refundOrderNo) {
       onConfirmReceipt(refundOrderNo).then(() => {
@@ -425,6 +435,8 @@ export default {
       this.tableFrom.content = '';
       this.tableFrom.searchType = 'all';
       this.tableFrom.trackingNumber = '';
+      this.tableFrom.merId = null;
+      this.timeVal = [];
       this.selectChange();
     },
     //搜索