Multi-language support

[BeautifulWorld-mrusu]

At the moment, Llama is only available in English. I, alongside many others, would appreciate support for more languages! This space is pretty empty.

[opastorello]

+1 for this, and I have a working implementation I'd be happy to turn into a PR if the maintainers are interested. Per the contributing guide I won't open one unless asked.

What it does

• Moves the user-facing strings into a String Catalog (Localizable.xcstrings), with Portuguese (Brazil) and Spanish as a first pass
• Follows the macOS language and falls back to English for anything else
• Adds a Language picker in Settings > General that lists whatever languages the bundle ships, so adding a language is only a new column in the catalog (no code change)
• Asks to restart when the language changes, since it applies at launch

Cost

• App size: the two translations add ~88 KB (about 1% of the app)
• Code: mostly mechanical, ~270 added lines across ~30 Swift files; the rest is the generated catalog
• Maintenance is the real cost: new UI strings need a translation per language, though untranslated ones fall back to English, so nothing breaks

Not covered: the built-in chat WebUI comes from llama.cpp and is English only, so it doesn't follow the app language.

The implementation is on my fork for reference, not as a PR: https://github.com/opastorello/Llama-macOS/tree/feat/localization

Happy to shrink the scope (a single extra language, no READMEs, no picker) if that fits the "easy wins" bar better.

[BeautifulWorld-mrusu]

I like this. I'd recommend Crowdin to ease the localization process.