chore(init): 初始化解忧商行项目并完成 Phase 0 基座

backend/internal/modules/chat/export.go

@@ -0,0 +1,36 @@
+package chat
+
+import (
+	"hfb_sys/backend/internal/model"
+
+	"gorm.io/gorm"
+)
+
+// DefaultSupportAdminID 导出默认客服选择逻辑，供其他业务模块建群时复用。
+func DefaultSupportAdminID(tx *gorm.DB) uint64 {
+	return defaultSupportAdminID(tx)
+}
+
+// SendSystemMessageForTx 在事务内发送系统文本消息。
+func SendSystemMessageForTx(tx *gorm.DB, conversationID uint64, content string) error {
+	return sendSystemMessage(tx, conversationID, content)
+}
+
+// SendImageMessageForTx 在事务内发送系统图片消息。
+func SendImageMessageForTx(tx *gorm.DB, conversationID uint64, content, imageURL string) error {
+	if content == "" {
+		content = "👇 请扫码联系客服"
+	}
+	message := model.ChatMessage{
+		ConversationID: conversationID,
+		SenderType:     "system",
+		SenderRole:     "system",
+		ContentType:    "image",
+		Content:        content,
+		AttachmentURLS: encodeStringList([]string{imageURL}),
+	}
+	if err := tx.Create(&message).Error; err != nil {
+		return err
+	}
+	return updateConversationLastMessage(tx, conversationID, &message)
+}