feature(mobile): add interface language switching

[JeffC0628]

What changed

The app's interface was hardcoded in English, with no way to use it in another language. This adds interface language switching to the Expo app (web, iOS, Android) with nine locales: English, Simplified Chinese, Traditional Chinese, Japanese, Korean, Spanish, Brazilian Portuguese, French, and German.

• apps/mobile/src/i18n/ sets up i18next and react-i18next with one JSON catalog per locale. English is the source and fallback. Keys are semantic, such as nav.chat or mail.noMatch.
• The language comes from the saved choice, then the device locale (expo-localization), then English. Regional tags map to the shipped catalogs: zh-TW/zh-HK/zh-MO use Traditional Chinese, other zh tags use Simplified Chinese, and pt-* uses Brazilian Portuguese.
• Apps → Personality & memory has a Language picker. Each option is written in its own language. Switching updates the interface immediately, is saved with AsyncStorage, and sets <html lang> on web.
• Dates, times, and relative times ("3 hours ago") use Intl with the active locale instead of en-US.
• Product and provider names stay as written: OpenMuse, Gmail, Google Calendar, OpenBot, Chromium, CopilotKit, plus format names such as PDF, JSON, URL, and CSV. They are interpolated from i18n/glossary.ts rather than repeated in each catalog.
• Content and data are not translated: server error messages, model prompts and replies, mail, calendar and page content, URLs, email addresses, time zone IDs, date input formats, the agent's default name, and stored values (only their labels are translated).

New dependencies, at Expo SDK 54 versions: expo-localization, i18next, react-i18next, @react-native-async-storage/async-storage.

Verification

Run locally on Windows 11 with Node 24 and pnpm 11.19.0.

• pnpm lint: passes on a clean LF checkout of this branch. In a Windows clone with core.autocrlf=true, Biome reports format errors for unchanged files checked out with CRLF (the issue addressed by chore: check text files out with LF so Windows clones pass lint #175). The changed files pass Biome in place.
• pnpm typecheck: the root tsc --noEmit and the apps/mobile typecheck both pass. I ran the two halves directly because the script's nested pnpm call is not on PATH in this shell.
• pnpm test: 482 pass, 2 fail, 3 skipped. Both failures are Windows environment issues outside the app:
  • worker recovery preserves downloads when metadata cannot be inspected fails with EPERM on symlink. It fails the same way on unmodified main.
  • fixture lifecycle releases its server when temporary profile creation fails failed under full-suite load and passed both times when run alone.
• New apps/mobile/test/locale.test.ts covers locale tag mapping, checks that every catalog has the same keys and {{placeholder}} names as English, and checks that dates follow the locale. relative-date.test.ts covers localized relative times.
• pnpm build:server, pnpm build:web, pnpm build:ios, pnpm build:android, and pnpm --dir apps/worker typecheck pass.
• Web, against pnpm dev:demo (sample workspace): with a Chinese system locale, the app opened in Simplified Chinese. Choosing 日本語 updated every visible label without a reload, set <html lang="ja">, and was kept after reloading. Product names stayed unchanged.

Screenshots:

Integration limits

• The non-English catalogs were machine-assisted and checked for placeholders, product names, and key coverage, but not reviewed by a native speaker of each language. Corrections are welcome.
• A few less common strings are still English: action review notes and approval buttons in details.tsx, the command hint, output toggle, and file messages in computer-workspace.tsx, the queue labels and client errors in chat.tsx, and a few notes in agent-ui.tsx.
• Server error messages remain English. Translating them needs stable error codes from the API.
• No right-to-left language is included, so RTL layout is untested.
• I did not run iOS or Android simulators. The platform exports pass, and the picker was checked on a phone-sized screen.