refactor: 미사용 코드 제거

src/main/kotlin/roomescape/admin/business/AdminService.kt

@@ -48,15 +48,4 @@ class AdminService(
             AuditConstant.UNKNOWN_OPERATOR
         }
     }
-
-    private fun findOrThrow(id: Long): AdminEntity {
-        log.info { "[AdminService.findOrThrow] 조회 시작: id=${id}" }
-
-        return adminRepository.findByIdOrNull(id)
-            ?.also { log.info { "[AdminService.findOrThrow] 조회 완료: id=${id}, name=${it.name}" } }
-            ?: run {
-                log.info { "[AdminService.findOrThrow] 조회 실패: id=${id}" }
-                throw AdminException(AdminErrorCode.ADMIN_NOT_FOUND)
-            }
-    }
 }

src/main/kotlin/roomescape/common/config/JacksonConfig.kt

@@ -57,30 +57,6 @@ class JacksonConfig {
         return simpleModule
     }
 
-    class LongToStringSerializer : JsonSerializer<Long>() {
-        override fun serialize(value: Long?, gen: JsonGenerator, serializers: SerializerProvider) {
-            if (value == null) {
-                gen.writeNull()
-            } else {
-                gen.writeString(value.toString())
-            }
-        }
-    }
-
-    class StringToLongDeserializer : JsonDeserializer<Long>() {
-        override fun deserialize(p: JsonParser, ctxt: DeserializationContext): Long? {
-            val text = p.text
-            if (text.isNullOrBlank()) {
-                return null
-            }
-            return try {
-                text.toLong()
-            } catch (_: NumberFormatException) {
-                throw RoomescapeException(CommonErrorCode.INVALID_INPUT_VALUE)
-            }
-        }
-    }
-
     class LocalDateTimeSerializer : JsonSerializer<LocalDateTime>() {
         override fun serialize(
             value: LocalDateTime,