fix: Complete Portuguese (Brazil) translation with missing fields (#800)

🎯 Goal
Ensure complete and accurate localization for Portuguese (Brazil) (pt-BR), resolving translation gaps from the initial implementation.

✅ Changes Made
* Updated `messages/pt-BR.json` to be fully synchronized with the `en.json` source file.
* Translated all missing keys, including critical sections that were previously untranslated (e.g., `settings.audio`, `recording`, `editor`, `footer`, and `article.editor.toolbar`).
* Ensured 100% key-for-key parity with the source language file to prevent UI fallbacks.

🔍 Context
The initial Portuguese translation (PR #726) was incomplete. This caused the UI to fall back to other languages (like Chinese Traditional) or display raw translation keys for Brazilian users. This PR provides the correct and complete translations to ensure a fully native experience.

🧪 Ready for Testing
All translation keys are properly mapped and ready for integration.

Thank you for reviewing this contribution! 🚀

Author: magisph