Initial scaffold: context-aware notes app for iOS + macOS

XcodeGen project (Notes / NotesMac / NotesTests), Swift 6 strict concurrency,
iCloud-document storage via IndieSync with a SwiftData cache, automatic
capture context (location, place, time zone, device) on every note,
context-based relevance ranking with a 'Right here, right now' shelf,
tags, search, and the square.and.pencil-on-red app icon.

.gitignore

@@ -0,0 +1,5 @@
+build/
+DerivedData/
+*.xcodeproj
+.DS_Store
+xcuserdata/