Implement Internationalization (i18n) for 13 Languages

Goal

Implement i18n infrastructure using @nuxtjs/i18n module to support 13 languages as used in production.

Priority

CRITICAL - Must be implemented FIRST as all UI components depend on translation capability.

Implementation Steps

1. Install @nuxtjs/i18n package
2. Configure in nuxt.config.ts with supported locales
3. Create locales/ directory with translation files
4. Start with EN and DE, add remaining 11 languages later
5. Update existing components to use $t() instead of hardcoded strings
6. Add language switcher component

Acceptance Criteria

• @nuxtjs/i18n installed and configured
• Translation files for EN and DE created
• All existing UI strings use i18n translations
• Language switching works correctly
• No missing translation warnings
• Documentation for adding new translations

Dependencies

None - this is the foundation for all other features

References

• Production app supports 13 languages
• Uses vue-i18n under the hood