[BE] fix: 미디움 발행 요청에 contentFormat 파라미터 추가

backend/src/main/java/org/donggle/backend/infrastructure/client/medium/MediumApiClient.java

@@ -54,6 +54,7 @@ private MediumRequestBody makePublishRequest(final String titleValue, final Stri
         return MediumRequestBody.builder()
                 .title(titleValue)
                 .content(content)
+                .contentFormat("html")
                 .tags(tags)
                 .build();
     }