The flat list of 6 languages plus 'system' dominated Settings. Replace it
with a single tile showing the current language, opening a bottom-sheet
picker (all languages + 'System language'). Resolve LocaleStore defensively
so the screen renders in DI-less widget tests.
- Add rtl_smoke_test covering inventory, detail (lot sheet) and settings
under Directionality.rtl, with an Arabic label and vernacular name.
- Ship pt.i18n.json (Portuguese) as proof the locale pipeline scales beyond
es/en; wire its language tile in Settings.
- docs/i18n.md documents the Weblate-ready flow for adding locales.
