Portuguese translate updates and locales-tool added

feat(i18n): add comprehensive localization support tool

Add a browser-based translation management tool to assist with
OldTwitter localization efforts. This tool provides:

- Side-by-side comparison of base (EN) and target translations
- Visual diff highlighting missing and extra translations
- Structural validation of locale files
- Dark/light mode support for extended usage
- JSON conversion utility for easy translation input
- Statistics dashboard showing translation progress

The tool supports all current OldTwitter locales and integrates
with the existing test.js validation system. Translators can now:
- Easily identify missing translations
- Validate JSON structure
- Convert plain text to proper locale format
- Track translation progress visually

Technical implementation:
- Pure JavaScript/HTML/CSS solution
- No external dependencies except jsdiff
- Offline-capable with static locale list
- Responsive design with accessibility considerations

Part of the ongoing effort to improve OldTwitter's
internationalization workflow.

feat(locales-tool): enhance dark mode and improve visual feedback

- Add dark mode support for diff container with semi-transparent background
- Fix contrast issues in diff section headers
- Improve visibility of added/removed status indicators
- Adjust text colors for better readability in both light/dark modes

Technical changes:
- Added specific styling for removed/added section headers
- Fixed color inheritance in dark mode
- Adjusted background opacity for better content visibility
- Maintained semantic meaning through color indicators

Note: Minor visual artifacts may occur in dark mode due to
CSS specificity, but core functionality remains intact.