[yurineves92]

Add Brazilian Portuguese (pt-BR) documentation translation

Following up on #545: instead of linking to a separate guide, this adds the Brazilian Portuguese translation to this repository.

Changes

• Added pt-BR to the po4a config
• Translated all pt-BR .po files (guide, cookbook and internals) and generated the Markdown in src/pt-BR
• Configured the pt-BR locale in VitePress (nav, sidebar, footer, search and outline labels)

Notes

• Code blocks are kept as they are; only comments and human-readable labels inside them are translated.
• GitHub alert markers ([!NOTE], [!TIP], ...) are kept untouched.
• In-page and cross-page anchors were updated to match the translated headings.
• Terminology follows the community guide I maintain in Portuguese (https://github.com/yurineves92/guia-yii3).

Commits are split by section to make review easier. npm run build passes locally.

Dead links

Since this PR touches every page under src/pt-BR, the link checker now runs on all of them, and it reported links that are broken in the English source too (and in every translation). The last commit fixes them at the source and applies the same change to every language's .po file, so no existing translation becomes fuzzy:

• Internal links to pages that don't exist: structure/handler.md now points to structure/action.md, domain.md/service.md point to their new place in the Cookbook (moved in The Domain and Service sections have been moved to the Cookbook #535), and the cookbook service page links to the guide's middleware page. Links to the unwritten caching pages (fragment.md, page.md, http.md) are now plain text.
• External links that are gone: APC → APCu docs, HTMLPurifier → its GitHub repository, OWASP pages → their current URLs, and the old guide/en path → src/guide.
• Sites that block the checker (403) or are unreachable from CI (dev.mysql.com, stackoverflow.com, security.stackexchange.com, code.tutsplus.com, yiiframework.ru) are added to ignorePatterns in .markdown-link-check.json.

[samdark]

👍

[samdark]

👍

[yurineves92]

Thanks for the review and merge, @samdark! I'll keep the pt-BR translation up to date as the English docs evolve. 🙏