H-337: restore Web widget reply visibility (#64)

* H-337: restore widget reply delivery

* H-337: harden widget conversation ownership

---------

Co-authored-by: Rogee <rogee@ipao.vip>

backend/internal/wsevent/bridge_listener_test.go

@@ -31,7 +31,9 @@ func (h *captureHub) SendToRoom(room string, data []byte) {
 func TestBridgeListenerRoutesWebWidgetEventsToDashboardAndVisitor(t *testing.T) {
 	event := channel.NewChannelEvent(channel.EventMessageCreated, channel.ChannelWebWidget, 1, 4)
 	event.Data["widget_token"] = "visitor-token"
+	displayID := uint(42)
 	event.Data["message"] = &model.Message{Base: model.Base{ID: 12}, AccountID: 1, InboxID: 4, ConversationID: 2, MessageType: "outgoing", SenderType: "User"}
+	event.Data["conversation"] = &model.Conversation{Base: model.Base{ID: 2}, DisplayID: &displayID}
 	event.Data["sender"] = &model.User{Base: model.Base{ID: 8}, Name: "Agent A"}
 
 	hub := &captureHub{}
@@ -53,6 +55,9 @@ func TestBridgeListenerRoutesWebWidgetEventsToDashboardAndVisitor(t *testing.T)
 	if payload["sender_type"] != "User" || payload["sender"].(map[string]interface{})["name"] != "Agent A" {
 		t.Fatalf("visitor reply sender contract mismatch: %#v", payload)
 	}
+	if payload["message_type"] != float64(1) || payload["conversation_id"] != float64(displayID) {
+		t.Fatalf("visitor reply message contract mismatch: %#v", payload)
+	}
 }
 
 func TestBridgeListenerPreservesWebWidgetSenderTypeContract(t *testing.T) {