优化发布群配置与二维码池界面

backend/internal/modules/chat/listing_group.go

@@ -189,14 +189,12 @@ func listingConversationTitle(listing model.RentalListing) string {
 }
 
 func getListingGroupWelcomeMessage(tx *gorm.DB) string {
-	defaultMsg := "欢迎加入账号群！请号主扫描下方二维码加入企业微信群，方便客服与您及时联系。"
-
 	var cfg model.SystemConfig
-	if err := tx.Where("`key` = ?", "chat.listing_group_welcome").First(&cfg).Error; err == nil && cfg.Value != "" {
+	if err := tx.Where("`key` = ?", listingGroupWelcomeConfigKey).First(&cfg).Error; err == nil && cfg.Value != "" {
 		return cfg.Value
 	}
 
-	return defaultMsg
+	return defaultListingGroupWelcome
 }
 
 func sendSystemMessage(tx *gorm.DB, conversationID uint64, content string) error {
@@ -218,7 +216,6 @@ func sendSystemMessage(tx *gorm.DB, conversationID uint64, content string) error
 }
 
 func sendQrCodeImage(tx *gorm.DB, conversationID uint64, imageURL string) error {
-	attachmentURLs := `["` + imageURL + `"]`
 	content := "👇 请扫码加入企业微信群"
 
 	message := model.ChatMessage{
@@ -227,7 +224,7 @@ func sendQrCodeImage(tx *gorm.DB, conversationID uint64, imageURL string) error
 		SenderRole:     "system",
 		ContentType:    "image",
 		Content:        content,
-		AttachmentURLS: []byte(attachmentURLs),
+		AttachmentURLS: encodeStringList([]string{imageURL}),
 	}
 
 	if err := tx.Create(&message).Error; err != nil {