✨ Migrate to String Catalogs

### Description

The project is using the deprecated .strings files internally. It should be migrated to String Catalogs by right-clicking and choosing migrate. It should really be as simple as that. Xcode should then pick up new localization keys from there using SwiftUI's built-in `LocalizedStringKey` type.

I could do it myself if I get the "Go" from the core maintainers.