Localization

[evansmj]

This issue is to add language translations to the app.

[ShahanaFarooqui]

Closing this for now. After looking into what proper i18n actually entails — maintaining translation files, pluralization edge cases, RTL support, keeping strings in sync across releases — the ongoing maintenance cost doesn't justify the investment at this stage.

Browser-native translation covers the majority of users who need this, and we don't have data suggesting localization is a meaningful drop-off point.

We will revisit if there is a strong user demand in future.