`readdir` returns entries in the filesystem's own order — inode order on ext4 —
which is arbitrary and stable only until somebody moves a file.
Harmless for the sync, which does the same work whatever the order. Not harmless
for "Create Gallery": that list becomes the gallery's initial order, and nine
photographs arriving as 05, 08, 01, 07 reads as a bug even though nothing is
wrong.
`numeric` collation, so galeria2 sorts before galeria10 — which is what anybody
naming files that way means.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>