fix(basic-pricing): 修复代金券码为空的问题

- 在 VoucherPrintServiceImpl 类中，为 existingRecord 对象添加代金券码
- 将 existingRecord 的 voucherCode 字段值赋给

src/main/java/com/ycwl/basic/pricing/service/impl/VoucherPrintServiceImpl.java

@@ -160,6 +160,7 @@ public class VoucherPrintServiceImpl implements VoucherPrintService {
         if (existingRecord == null) {
             return null;
         }
+        existingRecord.setCode(existingRecord.getVoucherCode());
         return buildResponse(existingRecord);
     }