WebUI localization

[ronaldmannak]

Would adding localization to the WebUI be of interest? The WebUI is currently English-only. Supporting a few additional languages could make it friendlier for non-English users.

Just to set expectations: full coverage will touch a lot of WebUI files, since every user-facing string needs to go through the i18n layer.

Proposed approach: runtime i18n that fetches static/locales/.json (same-origin) to keep the bundle size below 2 MB, initialized in src/routes/+layout.svelte, with language auto-detect and an optional localStorage override.

If this direction makes sense, I’m happy to open a draft PR so you can react to the approach before it grows. Do you have a preference between svelte-i18n and a tiny in-repo store, is runtime fetching of /locales/.json acceptable, and are there any languages that make sense to start with?