Add full Brazilian Portuguese locale support for the snippet viewer. Introduces brazilianPortugueseTranslations in translations.ts and registers it in the viewer DEFAULTS (imported in app.tsx). Update UI schema to include pt-BR in the wide-label-languages group (and clarify the comment). Update plugin-i18n docs for React, Snippet, Svelte and Vue to list Brazilian Portuguese (pt-BR) as a supported language.

Add a changeset and update vendored PDFium artifacts to fix callout FreeText annotations rendering with a black fill when the fill color is transparent. The GenerateFreeTextAP callout branch no longer paints the text-box unconditionally with operator `B`; the fill now defaults to transparent via GetColorStringWithDefault and the paint operator is selected with GetPaintOperatorString (matching GenerateCircleAP/GenerateSquareAP). Also updates the pdfium submodule and regenerated vendor bindings/artifacts (functions.ts, pdfium.cjs/js/wasm, runtime-methods.ts).