feat: stubs s3_upload, s3_download, s3_presign_url (issue 0014 fase 4)

functions/infra/s3_download.go

@@ -0,0 +1,17 @@
+package infra
+
+import (
+	"fmt"
+	"io"
+)
+
+// S3Download descarga el objeto identificado por key desde el bucket S3-compatible
+// y escribe su contenido en dst.
+//
+// STUB: la implementacion real requiere github.com/aws/aws-sdk-go-v2.
+func S3Download(cfg S3Config, key string, dst io.Writer) error {
+	_ = cfg
+	_ = key
+	_ = dst
+	return fmt.Errorf("s3_download: not implemented (requiere github.com/aws/aws-sdk-go-v2)")
+}