Sort the manga catalog by created / updated / title / author with an
independent asc/desc direction control. An omitted `order` defaults per field
(dates newest-first, text A→Z), matching the UI, so a bare `?sort=<field>`
means the same thing in the browser and over the API; `sort=recent` remains a
back-compat alias for `created`.
- Backend: SortField/SortOrder parsed with validation (structured 422 on bad
input), per-field default_order, NULLS LAST only on the nullable author key,
and migration 0033 indexing mangas(updated_at DESC, id) to back the default
sort and its id tie-break.
- Frontend: catalog sort field + direction (SegmentedControl) on desktop and a
mobile bottom sheet; pure helpers in $lib/mangaSort; keyboard-accessible
direction control; visible Direction labels and a sheet "Done" button.
- Tests: backend integration coverage (defaults, alias, invalid input,
ascending-id tie-break), frontend unit + e2e.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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