Re-apply "Refactor walkDirTree to use fs.FS" but remove context cancelation logic.

This reverts commit 6b3b4d83ff.

utils/paths.go

@@ -1,18 +0,0 @@
-package utils
-
-import (
-	"os"
-
-	"github.com/navidrome/navidrome/log"
-)
-
-func IsDirReadable(path string) (bool, error) {
-	dir, err := os.Open(path)
-	if err != nil {
-		return false, err
-	}
-	if err := dir.Close(); err != nil {
-		log.Error("Error closing directory", "path", path, err)
-	}
-	return true, nil
-}