修复selectById编译错误，改为selectDeptById

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

airport-admin/src/main/java/com/sundot/airport/web/controller/exam/DailyExamComparisonController.java

@@ -377,7 +377,7 @@ public class DailyExamComparisonController {
     }
 
     private String getDeptName(Long deptId) {
-        SysDept dept = sysDeptMapper.selectById(deptId);
+        SysDept dept = sysDeptMapper.selectDeptById(deptId);
         return dept != null ? dept.getDeptName() : "部门" + deptId;
     }