fix(storage): COS 资源下载 - 公开 CDN 模式使用附件响应头 (#718)

backend/internal/assets/access_test.go

@@ -140,15 +140,11 @@ func TestResolveAccessVariantAndExpiryContract(t *testing.T) {
 	}
 }
 
-func TestResolveDownloadUsesObjectOriginAttachmentInsteadOfCDNOrProxy(t *testing.T) {
+func TestResolveDownloadUsesPublicCDNAttachment(t *testing.T) {
 	now := time.Date(2026, time.January, 2, 3, 4, 5, 0, time.UTC)
 	resource := testReadyResource("aliyun")
 	setting := storage.Settings{
-		// A public IP keeps the test deterministic: PublicOrigin intentionally
-		// resolves hostnames to reject private DNS answers, so a made-up OSS host
-		// would depend on the machine's DNS configuration.
-		Provider: "aliyun", Endpoint: "https://1.1.1.1", Bucket: "private-bucket",
-		AccessKeyID: "access-id", AccessKeySecret: "secret-value", CDNBaseURL: "https://media.example.com",
+		Provider: "aliyun", CDNBaseURL: "https://media.example.com",
 		Delivery: storage.DeliverySettings{CDNAuthMode: "public"},
 	}
 	access, err := ResolveAccess(resource, setting, AccessOptions{Purpose: PurposeDownload, DownloadName: "画布_镜头01.mp4"}, now, testPlatformURL(&[]ResourceVariant{}))
@@ -160,7 +156,7 @@ func TestResolveDownloadUsesObjectOriginAttachmentInsteadOfCDNOrProxy(t *testing
 		t.Fatal(err)
 	}
 	disposition := parsed.Query().Get("response-content-disposition")
-	if access.Delivery != DeliveryOrigin || parsed.Host != "1.1.1.1" || !strings.HasPrefix(disposition, "attachment") || !strings.Contains(strings.ToLower(disposition), "utf-8''") {
+	if access.Delivery != DeliveryCDN || access.ExpiresAt != nil || parsed.Host != "media.example.com" || !strings.HasPrefix(disposition, "attachment") || !strings.Contains(strings.ToLower(disposition), "utf-8''") {
 		t.Fatalf("download access = %#v, disposition=%q", access, disposition)
 	}
 }