fix: prevent repeated off-hours handoff notices

internal/services/conversation_human_dispatch_service.go

@@ -58,6 +58,9 @@ func (s *conversationHumanDispatchService) TryOffHoursHandoffByAI(conversationID
 	if err := s.createEvent(conversationID, enums.IMEventTypeTransfer, enums.IMSenderTypeAI, aiAgent.ID, "转人工失败：非服务时间", strings.TrimSpace(reason)); err != nil {
 		return true, err
 	}
+	if s.hasLatestAIText(conversationID, HandoffOffHoursMessage) {
+		return true, nil
+	}
 	if err := s.sendAIText(conversationID, aiAgent.ID, HandoffOffHoursMessage); err != nil {
 		return true, err
 	}
@@ -288,6 +291,14 @@ func (s *conversationHumanDispatchService) sendAIText(conversationID, aiAgentID
 	return err
 }
 
+func (s *conversationHumanDispatchService) hasLatestAIText(conversationID int64, content string) bool {
+	latest, err := MessageService.GetConversationReadTarget(conversationID, 0)
+	if err != nil || latest == nil {
+		return false
+	}
+	return latest.SenderType == enums.IMSenderTypeAI && strings.TrimSpace(latest.Content) == strings.TrimSpace(content)
+}
+
 func orderedPositiveIDs(value string) []int64 {
 	return uniquePositiveInt64sFromStrings(strings.Split(value, ","))
 }