Add pt-br as a fifth interface language beside English, Simplified
Chinese, Traditional Chinese (Taiwan) and Japanese.
`crates/ui-egui/locales/pt-br.json` and `pt-br-formats.json` carry the
messages and the format strings; the language table gains the entry
(`PtBr, "pt-br", "Português (Brasil)", "Latn", ...`), and Edit > Language
plus `app.language.portuguese` select it. Locale tags pt-BR, pt_BR.UTF-8
and pt all normalize to the same language.
Translation follows pt-BR UI conventions (Adobe terms: revelação,
balanço de branco, máscara, cópia virtual…); proper nouns and file
formats stay as written (LightCraft, ArtCraft, GitHub, DNG, TIFF, XMP).
Placeholders, format specs and punctuation match the English source; the
English plural suffix is consumed with `{:.0}` where Portuguese does not
need it.
Tests: every_language_has_a_catalog_covering_the_source,
catalogs_agree_on_placeholders_and_report_gaps, locale_tags_normalize
and the painted-window test now cover pt-br. Docs: localization.md, a
new localization-pt-br.md and the parity rows.
Co-Authored-By: DeepSeek V4 Flash (opencode) <noreply@opencode.ai>
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