- Thumbnail jobs and the legacy scan_output_dir listing leave
library-removed files out (one mark check, mark_hides).
- Missing-file links also forgets removal marks that hide nothing any
more (file gone from a folder that exists, or changed), only under a
readable, non-empty source, re-checked at apply.
- The sidebar Images, Favorites and Needs review counts and the
collection counts are read again when an image_delete job ends.
- utils/media_folders.py: one skip for thumbnails and trash folders
(.Trash, .Trash-<uid>, .Trashes, $RECYCLE.BIN) used by every walker,
the image monitor and the delete review.