Tasks: App Localization (Automatic System Language Detection)

[x] Install i18next-browser-languagedetector.
[x] Update src/localization/i18n.ts to configure language detection and include zh-CN resources.
[x] Verify src/actions/language.ts logic is compatible with auto-detection.
[x] Update src/components/StatusBar.tsx to use translations.
[x] Update src/components/AccountCard.tsx to use translations.
[x] Update src/pages/index.tsx (home page) to use translations.
[x] Update src/pages/settings.tsx to use translations and add a language switcher.
[x] Run the app to verify language detection and manual switching.