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.

Notes/Views/App/ContentView.swift

@@ -0,0 +1,25 @@
+import SwiftUI
+
+struct ContentView: View {
+    @Environment(SyncEngine.self) private var syncEngine
+
+    var body: some View {
+        if syncEngine.iCloudStatus == .unavailable {
+            ICloudGateView()
+        } else {
+            TabView {
+                Tab("Notes", systemImage: "square.and.pencil") {
+                    NotesListView()
+                }
+
+                Tab("Tags", systemImage: "tag") {
+                    TagsView()
+                }
+
+                Tab("Settings", systemImage: "gearshape") {
+                    SettingsView()
+                }
+            }
+        }
+    }
+}