feat(cluster): 增加跨节点任务执行与请求素材场景

新增 AI_GATEWAY_ASYNC_QUEUE_WORKER_ENABLED，默认保持启用；关闭时仅停止 River 异步任务执行器，HTTP、健康检查、结算与其他后台任务继续运行。

新增 0089 迁移并同步管理端默认场景，将 request_asset 加入现有上传渠道，确保 multipart 请求素材先转换为跨节点共享 URL。

验证：gofmt、go test ./... -count=1、go vet ./...、pnpm lint、pnpm test、pnpm build、迁移测试。

apps/api/internal/store/file_storage_channels.go

@@ -578,7 +578,7 @@ func normalizeFileStorageScene(scene string) string {
 }
 
 func defaultFileStorageScenes() []string {
-	return []string{FileStorageSceneUpload, FileStorageSceneImageResult}
+	return []string{FileStorageSceneUpload, FileStorageSceneImageResult, FileStorageSceneRequestAsset}
 }
 
 func defaultFileStorageRetryPolicyIfEmpty(policy map[string]any) map[string]any {

apps/api/internal/store/file_storage_channels_test.go

@@ -0,0 +1,17 @@
+package store
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestDefaultFileStorageScenesIncludeCrossNodeRequestAssets(t *testing.T) {
+	want := []string{
+		FileStorageSceneUpload,
+		FileStorageSceneImageResult,
+		FileStorageSceneRequestAsset,
+	}
+	if got := defaultFileStorageScenes(); !reflect.DeepEqual(got, want) {
+		t.Fatalf("default file storage scenes = %#v, want %#v", got, want)
+	}
+}