BE: Set default message polling mode

address review comments

Author: wernerdv

api/src/main/java/io/kafbat/ui/controller/MessagesController.java

@@ -118,7 +118,7 @@ public Mono<ResponseEntity<Flux<TopicMessageEventDTO>>> getTopicMessagesV2(Strin
     if (cursor != null) {
       messagesFlux = messagesService.loadMessages(getCluster(clusterName), topicName, cursor);
     } else {
-      var pollingMode = mode == null ? PollingModeDTO.EARLIEST : mode;
+      var pollingMode = mode == null ? PollingModeDTO.LATEST : mode;
       messagesFlux = messagesService.loadMessages(
           getCluster(clusterName),
           topicName,