feat(i18n): Add internationalization support with English and Chinese

[Yeluo10123]

Summary

• Add i18next internationalization framework
• Add English (en) and Chinese (zh) translation files
• Create LanguageSwitcher component for runtime language switching
• Integrate i18n initialization in app.tsx

Translation Structure

Translations are organized by feature:

• common: Common UI elements (buttons, labels)
• home: Dashboard/home page
• menu: Navigation menu items
• maps: Maps feature
• chat: AI chat feature
• settings: Settings pages
• system: System settings
• apps: App management
• models: AI models
• easySetup: Setup wizard
• docs: Documentation
• about: About page
• errors: Error pages

Usage

Components can use translations like:

import { useTranslation } from 'react-i18next'

function MyComponent() {
  const { t } = useTranslation()
  return <button>{t('common.save')}</button>
}

Language Switcher

A LanguageSwitcher component is provided that can be added to the settings UI for users to switch between English and Chinese.

Next Steps

• Add LanguageSwitcher to settings UI
• Translate remaining hardcoded strings in page components
• Add more languages (e.g., Spanish, French)

🤖 Generated with Claude Code

[chriscrosstalk]

Thanks for the substantial work on i18n here. Quick status update so you know where this stands:

There are currently three open i18n PRs using two different frameworks (#490 with react-i18next + Portuguese, #518 with react-i18next + German, #648 with plain i18next + Chinese), each covering a different language. Before landing any i18n work, we need to make a framework decision so we end up with one coherent approach rather than a mix of incompatible implementations.

i18n isn't in scope for the next release cycle. It's on the roadmap for a future release, but no firm timeline.

What this means for your PR:

• No rush to rebase against current dev — these are long-lived PRs
• The framework decision will happen when we have capacity to actually integrate i18n, not before
• We'll coordinate a single direction with all three contributors when that time comes
• Your translation work is genuinely valued — we don't want to waste it by forcing a premature decision between branches

Leaving this open and labeling as Roadmap Item. Thanks for your patience and for contributing to NOMAD's international reach.