优化发布群租客清退与历史消息

backend/internal/modules/chat/listing_group.go

@@ -150,7 +150,8 @@ func AddRenterToListingConversation(tx *gorm.DB, listingID uint64, renterID uint
 		ParticipantType: "user",
 		ParticipantID:   renterID,
 		Role:            "renter",
-		JoinedAt:        now, // 关键: 记录加入时间,用于消息可见性过滤
+		JoinedAt:        now,
+		LastReadAt:      &now,
 	}
 
 	if err := tx.Clauses(clause.OnConflict{DoNothing: true}).Create(&participant).Error; err != nil {
@@ -183,17 +184,17 @@ func AddRenterToListingConversation(tx *gorm.DB, listingID uint64, renterID uint
 	return sendSystemMessage(tx, conv.ID, message)
 }
 
-// RemoveRenterFromListingConversation 移出租客
-func RemoveRenterFromListingConversation(tx *gorm.DB, listingID uint64, renterID uint64) error {
+// RemoveRenterFromListingConversation 移出租客，返回是否真的删除了租客成员记录。
+func RemoveRenterFromListingConversation(tx *gorm.DB, listingID uint64, renterID uint64) (bool, error) {
 	// 1. 查找发布群
 	var conv model.ChatConversation
 	err := tx.Where("listing_id = ?", listingID).First(&conv).Error
 	if err != nil {
 		if errors.Is(err, gorm.ErrRecordNotFound) {
 			// 无发布群,跳过
-			return nil
+			return false, nil
 		}
-		return err
+		return false, err
 	}
 
 	// 2. 删除租客参与者记录
@@ -202,16 +203,19 @@ func RemoveRenterFromListingConversation(tx *gorm.DB, listingID uint64, renterID
 		Delete(&model.ChatParticipant{})
 
 	if result.Error != nil {
-		return result.Error
+		return false, result.Error
 	}
 
 	// 3. 发系统消息(如果确实删除了)
 	if result.RowsAffected > 0 {
 		message := "订单已结束，租客已退出群聊"
-		return sendSystemMessage(tx, conv.ID, message)
+		if err := sendSystemMessage(tx, conv.ID, message); err != nil {
+			return false, err
+		}
+		return true, nil
 	}
 
-	return nil
+	return false, nil
 }
 
 // 辅助函数