fix(api): 分离异步队列入队与执行开关

AI_GATEWAY_ASYNC_QUEUE_WORKER_ENABLED=false 时仍初始化 River schema 与控制客户端，允许 HTTP 请求持久化并入队；仅跳过执行客户端和动态容量 Worker。关闭上下文时同步清理控制客户端引用。\n\n新增数据库集成测试覆盖无执行 Worker 时成功创建 River job 且 attempted_by 为空。验证：gofmt、go test ./... -count=1、go vet ./...。

apps/api/internal/runner/queue_worker.go

@@ -78,13 +78,20 @@ func (w *asyncTaskWorker) Work(ctx context.Context, job *river.Job[asyncTaskArgs
 }
 
 func (s *Service) StartAsyncQueueWorker(ctx context.Context) {
-	if err := s.startRiverQueue(ctx); err != nil {
+	if err := s.startRiverQueue(ctx, true); err != nil {
 		s.logger.Error("start river async queue failed", "error", err)
 		panic(err)
 	}
 }
 
-func (s *Service) startRiverQueue(ctx context.Context) error {
+func (s *Service) StartAsyncQueueClient(ctx context.Context) {
+	if err := s.startRiverQueue(ctx, false); err != nil {
+		s.logger.Error("start river async queue client failed", "error", err)
+		panic(err)
+	}
+}
+
+func (s *Service) startRiverQueue(ctx context.Context, workerEnabled bool) error {
 	driver := riverpgxv5.New(s.store.Pool())
 	migrator, err := rivermigrate.New(driver, nil)
 	if err != nil {
@@ -102,6 +109,23 @@ func (s *Service) startRiverQueue(ctx context.Context) error {
 	if err != nil {
 		return err
 	}
+	if !workerEnabled {
+		s.riverMu.Lock()
+		s.riverControlClient = controlClient
+		s.riverExecutionClient = nil
+		s.riverWorkerCapacity = 0
+		s.riverDrainingClients = make(map[asyncExecutionClient]struct{})
+		s.riverMu.Unlock()
+		if err := s.recoverAsyncRiverJobs(ctx); err != nil {
+			s.riverMu.Lock()
+			s.riverControlClient = nil
+			s.riverMu.Unlock()
+			return err
+		}
+		go s.stopAsyncWorkersOnShutdown(ctx)
+		s.logger.Info("river async queue client initialized without execution workers")
+		return nil
+	}
 	snapshot, err := s.loadAsyncWorkerCapacity(ctx)
 	if err != nil {
 		return fmt.Errorf("calculate initial async worker capacity: %w", err)
@@ -271,6 +295,7 @@ func (s *Service) drainAsyncWorkerClient(client asyncExecutionClient) {
 func (s *Service) stopAsyncWorkersOnShutdown(ctx context.Context) {
 	<-ctx.Done()
 	s.riverMu.Lock()
+	s.riverControlClient = nil
 	clients := make([]asyncExecutionClient, 0, 1+len(s.riverDrainingClients))
 	if s.riverExecutionClient != nil {
 		clients = append(clients, s.riverExecutionClient)