refactor: N+1 problem 해결(query 수정)

src/main/java/com/example/cp_main_be/domain/social/follow/domain/repository/FollowRepository.java

@@ -5,14 +5,30 @@
 import java.util.List;
 import java.util.Optional;
 import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Query;
+import org.springframework.data.repository.query.Param;
 
 public interface FollowRepository extends JpaRepository<Follow, Long> {
   Optional<Follow> findByFollowerAndFollowing(User follower, User following);
 
   List<Follow> findByFollower(User follower);
 
+  @Query(
+      "SELECT f FROM Follow f "
+          + "JOIN FETCH f.following u "
+          + "LEFT JOIN FETCH u.avatarList "
+          + "WHERE f.follower = :follower")
+  List<Follow> findByFollowerWithFollowingAndAvatars(@Param("follower") User follower);
+
   List<Follow> findByFollowing(User following);
 
+  @Query(
+      "SELECT f FROM Follow f "
+          + "JOIN FETCH f.follower u "
+          + "LEFT JOIN FETCH u.avatarList "
+          + "WHERE f.following = :following")
+  List<Follow> findByFollowingWithFollowerAndAvatars(@Param("following") User following);
+
   boolean existsByFollowerAndFollowing(User follower, User following);
 
   void deleteByFollowerAndFollowing(User follower, User following);

src/main/java/com/example/cp_main_be/domain/social/follow/service/FollowService.java

@@ -87,7 +87,9 @@ public List<FollowResponseDTO> getFollowers(Long userId) {
             .orElseThrow(() -> new CustomApiException(ErrorCode.USER_NOT_FOUND, "사용자를 찾을 수 없습니다."));
 
     List<User> userList =
-        followRepository.findByFollowing(user).stream().map(Follow::getFollower).toList();
+        followRepository.findByFollowingWithFollowerAndAvatars(user).stream()
+            .map(Follow::getFollower)
+            .toList();
 
     return userList.stream()
         .map(
@@ -109,8 +111,11 @@ public List<FollowResponseDTO> getFollowing(Long userId) {
         userRepository
             .findById(userId)
             .orElseThrow(() -> new CustomApiException(ErrorCode.USER_NOT_FOUND, "사용자를 찾을 수 없습니다."));
+
     List<User> userList =
-        followRepository.findByFollower(user).stream().map(Follow::getFollowing).toList();
+        followRepository.findByFollowerWithFollowingAndAvatars(user).stream()
+            .map(Follow::getFollowing)
+            .toList();
 
     return userList.stream()
         .map(