Add an iPhone client sharing the macOS app's SwiftUI code

mac/Sources/Byre/Notifications.swift

@@ -1,4 +1,4 @@
-import AppKit
+import SwiftUI
 import UserNotifications
 
 @MainActor
@@ -11,7 +11,9 @@ final class Notifier: NSObject, UNUserNotificationCenterDelegate {
     }
 
     private func open(_ origin: String, _ taskId: String) {
+        #if os(macOS)
         NSApp.activate()
+        #endif
         Servers.shared.show(origin)
         pending = (origin, taskId)
         deliver()