提交2: 发布群核心功能实现

- 实现 EnsureListingConversation: 发布时建发布群,发欢迎语+二维码
- 实现 AddRenterToListingConversation: 付款后拉租客进群
- 实现 RemoveRenterFromListingConversation: 订单终态移出租客
- 实现消息可见性过滤: 租客只能看到 joined_at 之后的消息
- listing 模块注入 ListingChatCreator 接口,发布时建群
- ListingDTO 新增 listing_group_conversation_id 字段
- 付款流程改为拉租客进发布群(替代建订单群)
- 订单完成和取消时自动移出租客
- 创建 chat 适配器实现接口解耦

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/internal/router/router.go

@@ -151,10 +151,7 @@ func New(cfg config.Config, deps Dependencies, logger *zap.Logger) *gin.Engine {
 	}
 	realnameService := realname.NewService(realnameRepo, newRealnameProvider(cfg, fieldEncryptor, logger), logger)
 	realnameHandler := realname.NewHandler(realnameService)
-	var listingRepo *listing.Repository
-	if deps.DB != nil {
-		listingRepo = listing.NewRepository(deps.DB)
-	}
+
 	var chatHub *chathub.Hub
 	if deps.DB != nil {
 		chatHub = chathub.NewHub(deps.DB)
@@ -163,6 +160,14 @@ func New(cfg config.Config, deps Dependencies, logger *zap.Logger) *gin.Engine {
 	if deps.DB != nil {
 		chatRepo = chat.NewRepository(deps.DB, chatHub)
 	}
+
+	// 创建 chat 适配器用于 listing
+	chatCreator := chat.NewListingChatCreatorAdapter()
+
+	var listingRepo *listing.Repository
+	if deps.DB != nil {
+		listingRepo = listing.NewRepository(deps.DB, chatCreator)
+	}
 	var paymentRepo *payment.Repository
 	var orderRepo *order.Repository
 	if deps.DB != nil {