Integrate Multilingual Support with next-intl and Crowdin

[joaoc-dev]

Set up internationalization (i18n) using next-intl and integrate Crowdin for translation management.
Include GitHub workflows to automate syncing translations between the codebase and Crowdin.

1. Set Up next-intl
2. Refactor App for i18n replacing hardcoded strings
3. Refactor next/link with next-intl/link for automatic locale handling.
4. Refactor router.push(..., { locale }) to navigate programmatically.
5. Integrate Crowdin
6. Configure GitHub workflow to maintain updated translations
7. Update README with developer instructions

Configure at least two languages and temporarily place a dropdown on the nav-bar that allows switching.