[Feature] Internationalization (i18n) framework & Simplified Chinese (zh-CN) localization for GUI

[AnonyJcy]

Hi @timhartmann7,

Thanks for building OmnySSH!

I put together an i18n setup for the GUI along with a full Simplified Chinese translation (zh-CN). Everything was kept lightweight using Svelte stores under $lib/i18n with zero external dependencies, following the existing codebase conventions.

Summary of changes:

• Type-safe translation dictionary and store in src/lib/i18n/
• Language selector added to Settings (English / 简体中文) with local persistence
• Localized components and screens: Dashboard, HostEditor, SFTP browser, Snippets, SSH Key setup, Command Palette, etc.
• All 225 unit tests pass, plus type-check passes with 0 errors/warnings (npm run check & npm test)

Would you be interested in taking a PR for this upstream? If so, I'm happy to open a clean pull request for review.

[timhartmann7]

Hi, that sounds interesting, open a PR i take a look when i can. This will actually be the starting point for adding other languages