Fill the ~74 UI strings pt.i18n.json was missing (saved searches, label
scanning, Plantaré, lot history), then add pt_BR as a proper Brazilian
variant rather than a copy of European Portuguese: tu/teu/tua -> você/
seu/sua with matching verb conjugation, partilhar -> compartilhar, and
Guardar -> Salvar for UI actions (seed-saving keeps "guardar", the
correct term in both variants). Wires AppLocale.ptBr into the language
picker and regenerates slang output.
