Implemented shared S3 audio caching for prepare and restore --include-audio

internal/adapters/storage/fake.go

@@ -27,8 +27,9 @@ type FakeBackend struct {
 	Err      error
 	Result   ArchiveResult
 
-	Objects map[string]FakeObject
-	Uploads []FakeUploadCall
+	Objects   map[string]FakeObject
+	Uploads   []FakeUploadCall
+	Downloads []FakeDownloadCall
 
 	ListErr     error
 	DownloadErr error
@@ -43,6 +44,12 @@ type FakeUploadCall struct {
 	Options   UploadOptions
 }
 
+// FakeDownloadCall captures one download invocation in call order.
+type FakeDownloadCall struct {
+	Key       string
+	LocalPath string
+}
+
 // Archive records request and returns configured response.
 func (f *FakeBackend) Archive(ctx context.Context, req ArchiveRequest) (ArchiveResult, error) {
 	if err := ctx.Err(); err != nil {
@@ -130,6 +137,10 @@ func (f *FakeBackend) Download(ctx context.Context, key, localPath string) error
 	if !ok {
 		return fmt.Errorf("download object %q: %w", key, os.ErrNotExist)
 	}
+	f.Downloads = append(f.Downloads, FakeDownloadCall{
+		Key:       normalizeObjectKey(key),
+		LocalPath: localPath,
+	})
 
 	if err := os.MkdirAll(filepath.Dir(localPath), 0o755); err != nil {
 		return fmt.Errorf("download object %q: create parent directory: %w", key, err)