feat: approval workflow with approver/backupApprover

backend/src/main/java/com/srsystem/service/EmployeeService.java

@@ -65,6 +65,11 @@ public class EmployeeService {
         return results;
     }
 
+    public List<EmployeeSearchResult> getApprovers() {
+        return employeeRepository.findByRoleCodeIn(List.of(RoleCode.MANAGER, RoleCode.ADMIN))
+                .stream().map(this::toSearchResult).toList();
+    }
+
     private EmployeeSearchResult toSearchResult(Employee e) {
         return new EmployeeSearchResult(
                 e.getEmpId(),
@@ -107,6 +112,8 @@ public class EmployeeService {
         employee.setProfileImage(updateRequest.getProfileImage());
         employee.setSchoolName(updateRequest.getSchoolName());
         employee.setPosition(updateRequest.getPosition());
+        employee.setManagerId(updateRequest.getManagerId());
+        employee.setBackupManagerId(updateRequest.getBackupManagerId());
 
         return employee;
     }