delete_gallery_image() deleted the on-disk file before setting
is_active=False and committing. If that commit failed and rolled back,
the record stayed active but its file was already gone — a broken,
unviewable image (data loss).
Soft-delete and commit first, then remove the file best-effort, so a
missing or locked file can no longer 500 a delete that already succeeded
logically.
Adds tests/test_gallery_delete_file_ordering.py covering the
commit-failure (file kept) and success (file removed) paths.
Mazen Tamer Salah