docs(pt): add full Portuguese translation

[sirtbot]

Translate all Web Docs, Web API, Game Docs, Game SDK pages and the homepage into Portuguese (pt-PT), add the pt locale and pt sidebar labels in astro.config.mjs, and list Portuguese in the README. "VTC" is kept untranslated per project convention.

Summary

• 64 new files under src/content/docs/pt/ (homepage, web-docs, web-api, game-docs, game-sdk)
• version copied from each English page, lastUpdated: 2026-09-21
• Internal links and heading anchors point to the /pt/ locale
• astro.config.mjs: new pt locale + Portuguese labels for every sidebar entry
• npm run validate and npm run build pass locally

Notes for reviewers

• Portuguese from Portugal (pt-PT) spelling, informal "tu" form, matching the tone of the German translation
• Literal UI labels (buttons/menu items) are kept in English, as the German translation does
• Program names ("Bug Hunters", "Contributors") are kept in English

🤖 Generated with Claude Code

[sirtbot]

Reviewed Manual