Restructure the project - use folder, folder structure, latest Xcode style

[yo1995]

Xcode 14 has changed the multiplatform app template to put everything in the same folder, instead of separating them into Shared, iOS, macOS, etc. as in Xcode 12 and 13. We shall decide which structure suits the project the best.

[yo1995]

Follow the Apple WWDC22 example: https://github.com/apple/sample-food-truck

[yo1995]

Consider moving the whole project to folder instead of group reference as Xcode 16 support is added.