refactor: WishlistResponseDto를 MyBarItemResponseDto로 리팩토링

- WishlistResponseDto 클래스를 MyBarItemResponseDto로 명칭 변경
- DTO가 사용자(User) 정보 대신 킵한 칵테일(Cocktail) 정보를 직접 포함하도록 수정

Author: MEOHIN

src/main/java/com/back/domain/mybar/dto/MyBarItemResponseDto.java

@@ -0,0 +1,27 @@
+package com.back.domain.mybar.dto;
+
+import com.back.domain.mybar.entity.MyBar;
+import lombok.Builder;
+import lombok.Getter;
+
+import java.time.LocalDateTime;
+
+@Getter
+@Builder
+public class MyBarItemResponseDto {
+    private Long id;
+    private Long cocktailId;
+    private String cocktailName;
+    private String imageUrl;
+    private LocalDateTime createdAt;
+
+    public static MyBarItemResponseDto from(MyBar m) {
+        return MyBarItemResponseDto.builder()
+                .id(m.getId())
+                .cocktailId(m.getCocktail().getCocktailId())
+                .cocktailName(m.getCocktail().getCocktailName())
+                .imageUrl(m.getCocktail().getImageUrl())
+                .createdAt(m.getCreatedAt())
+                .build();
+    }
+}