refactor(service): 불필요한 코드 제거 및 변수명 변경

- `findVolunteer`와 `findVolunteerDetail` 메서드 제거
  - 사용되지 않는 메서드로 판단하여 삭제
- `NEWVolunteerRepository` 변수명을 `volunteerRepository`로 변경
  - 가독성 및 네이밍 일관성 강화

src/main/java/com/somemore/domains/volunteer/service/VolunteerQueryService.java

@@ -1,7 +1,6 @@
 package com.somemore.domains.volunteer.service;
 
 import com.somemore.domains.volunteer.domain.Volunteer;
-import com.somemore.domains.volunteer.domain.VolunteerDetail;
 import com.somemore.domains.volunteer.dto.response.VolunteerRankingResponseDto;
 import com.somemore.domains.volunteer.repository.VolunteerDetailRepository;
 import com.somemore.domains.volunteer.repository.VolunteerRepository;
@@ -70,15 +69,4 @@ public void validateVolunteerExists(UUID volunteerId) {
             throw new BadRequestException(NOT_EXISTS_VOLUNTEER.getMessage());
         }
     }
-
-    private Volunteer findVolunteer(UUID volunteerId) {
-        return volunteerRepository.findById(volunteerId)
-                .orElseThrow(() -> new BadRequestException(NOT_EXISTS_VOLUNTEER));
-    }
-
-    private VolunteerDetail findVolunteerDetail(UUID volunteerId) {
-        return volunteerDetailRepository.findByVolunteerId(volunteerId)
-                .orElseThrow(() -> new BadRequestException(NOT_EXISTS_VOLUNTEER));
-    }
-
 }

src/main/java/com/somemore/volunteer/service/RegisterNEWVolunteerService.java

@@ -14,12 +14,12 @@
 @Transactional
 public class RegisterNEWVolunteerService implements NEWRegisterVolunteerUseCase {
 
-    private final NEWVolunteerRepository NEWVolunteerRepository;
+    private final NEWVolunteerRepository volunteerRepository;
 
     @Override
     public void register(UUID userId) {
         NEWVolunteer volunteer = NEWVolunteer.createDefault(userId);
 
-        NEWVolunteerRepository.save(volunteer);
+        volunteerRepository.save(volunteer);
     }
 }