Add Vietnamese (vi-VN) language support

[vuvtdhh]

Pull Request

Description

Add Vietnamese (vi-VN) language support

Key changes:

• Added option in lib/i18n.ts for i18n for local file map.
• Added i18n/locales/vi-VN.json containing Vietnamese translations.
• Added option in components/language-switcher.tsx to allow users toggle to Vietnamese.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Code refactoring
• Performance improvement
• Test improvements
• Security fix

Testing

• Unit tests added/updated
• Manual testing completed

pnpm test:run

Checklist

• Code follows the project's style guidelines
• Self-review completed
• TypeScript types are properly defined
• All commit messages are in English (Conventional Commits)
• All existing tests pass
• No new dependencies added, or they are justified

Related Issues

Closes #

Screenshots

Additional Notes