[Feedback]: Add multi-language (i18n) support to the desktop app

What problem are you trying to solve?

The desktop app currently ships with an English-only UI. Users who are not fluent in English (Simplified Chinese, Turkish, Japanese, Korean, Spanish, etc.) struggle to discover and understand features, which hurts onboarding and daily usage.

There are already several separate requests asking for individual locales - #43 (Turkish), #47, #53 and #74 (Simplified Chinese) - which clearly shows real demand. But each request only covers one language, and the underlying gap is that the app has no i18n/localization framework at all, so users cannot switch the interface language.

What would improve it?

Add a proper internationalization (i18n) layer to the desktop app:

• Externalize all user-facing strings into locale resource files (e.g. JSON) instead of hardcoding English in components.
• • Detect the OS/system language on first launch and add a Language selector in Settings to override it, applied without restart if possible.
• • • Ship an initial set of locales, at minimum Simplified Chinese (zh-CN), plus a documented way for the community to contribute new translations.
• • • • Localize dates, numbers and relative times, not just labels.
• • • • • Keep it extensible so more languages (Turkish, Japanese, Korean, Spanish, ...) can be added later.
          This single change would resolve the multiple one-off localization requests and give all non-English users a first-class experience.

What do you do today?

Today the UI is English-only and there is no language option in Settings. Users either work in English or look for unofficial patches. Related issues: #43, #47, #53, #74.

Product area

Settings

Start by mapping the desktop app's settings and user-facing UI entry points, then determine how language selection and system-language detection are currently handled. Done means an extensible localization layer, initial Simplified Chinese support, a Settings language selector, localized dates and numbers, and documented translation contributions.