A file past the size limit makes the multipart stream itself throw, which
escaped the per-file catch and reached the error handler: the phone that just
sent a 35 MB photo got 'Something went wrong'. Catch the limit errors around the
part loop, say which limit was hit, and report it once rather than twice. Also
asserts that derivatives carry no EXIF while the Original keeps the uploaded
bytes.
The store keeps a Menu Set's state in the directory layout (drafts/ versus
published/) and its metadata in a manifest, with publishing as a single
directory rename. Editing is allowed on Drafts only, so a published menu can
never change under a customer. Stages 2 and 3 of docs/plan.md, with tests.
tanshu