refactor: blacklist 엔티티의 jti에 인덱스를 건다. (#74)

Author: johnhuh619

src/main/java/sevenstar/marineleisure/global/jwt/BlacklistedRefreshToken.java

@@ -9,7 +9,10 @@
 import java.time.LocalDateTime;
 
 @Entity
-@Table(name = "blacklisted_refresh_tokens")
+@Table(name = "blacklisted_refresh_tokens", 
+       indexes = {
+           @Index(name = "idx_blacklisted_refresh_tokens_jti", columnList = "jti")
+       })
 @Getter
 @NoArgsConstructor
 public class BlacklistedRefreshToken extends BaseEntity {