resolveLocalFile swallowed every os.Open error, so uploads, playlist
sidecars, a local M3U image and the artist image folder still had the
bug that was fixed for folder and embedded sources: a permission or
transient I/O error on a file that exists read as "no image here". The
worker then settled the item absent and dropped its queue row.
Uploads outrank every other source, so an unreadable one now stops the
chain rather than letting a lower-priority image be persisted in its
place. A genuinely missing file stays a clean miss.
Reported by Codex on #5847.
6cd12e6070