refactor: split backend into standalone server project

Remove embedded frontend and workflow editor assets, add standalone API deployment configuration, and retain the current backend service updates.

internal/services/channel_service_test.go

@@ -48,6 +48,23 @@ func TestChannelServiceAllowsAgentWithPublishedRevision(t *testing.T) {
 	}
 }
 
+func TestChannelServiceAllowsHumanReceptionWithoutAIAgent(t *testing.T) {
+	setupChannelServiceTestDB(t)
+
+	item, err := ChannelService.CreateChannel(request.CreateChannelRequest{
+		ChannelType: enums.ChannelTypeWeb,
+		AIAgentID:   0,
+		Name:        "人工客服渠道",
+		Status:      int(enums.StatusOk),
+	}, channelServiceTestOperator())
+	if err != nil {
+		t.Fatalf("create human channel: %v", err)
+	}
+	if item == nil || item.AIAgentID != 0 {
+		t.Fatalf("unexpected human channel: %#v", item)
+	}
+}
+
 func TestChannelServiceStoresAIAgentRolloutPercent(t *testing.T) {
 	db := setupChannelServiceTestDB(t)
 	agent := createChannelServiceTestAgent(t, db, 1001)