fix(credit): 移除重复的唯一标识空值校验

- 删除了导入Excel时对项目唯一标识的非空校验逻辑
- 保留了项目名称的必填校验
- 简化了数据导入校验流程

src/main/java/com/gxwebsoft/credit/controller/CreditUserController.java

@@ -197,10 +197,6 @@ public class CreditUserController extends BaseController {
                         errorMessages.add("第" + excelRowNumber + "行：项目名称不能为空");
                         continue;
                     }
-                    if (item.getCode() == null || item.getCode().trim().isEmpty()) {
-                        errorMessages.add("第" + excelRowNumber + "行：唯一标识不能为空");
-                        continue;
-                    }
 
                     if (creditUserService.save(item)) {
                         successCount++;