Add iOS app with CarPlay and Siri

SwiftUI port of the Android app under ios/, with CarPlay browse and
Now Playing, Siri play-media intents, and a build-ipa.sh script that
makes an unsigned IPA for sideloading. README gets an iOS section and
the vibecoded disclaimer.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

ios/Stemify/App/StemifyApp.swift

@@ -0,0 +1,42 @@
+import AVFoundation
+import Intents
+import SwiftUI
+import UIKit
+
+final class AppDelegate: NSObject, UIApplicationDelegate {
+    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]? = nil) -> Bool {
+        try? AVAudioSession.sharedInstance().setCategory(.playback, mode: .default, policy: .longFormAudio)
+        MainActor.assumeIsolated { _ = AppGraph.shared }
+        return true
+    }
+
+    /// Phone windows go to SwiftUI; CarPlay gets its own scene delegate.
+    func application(_ application: UIApplication, configurationForConnecting session: UISceneSession, options: UIScene.ConnectionOptions) -> UISceneConfiguration {
+        if session.role == .carTemplateApplication {
+            let c = UISceneConfiguration(name: "CarPlay", sessionRole: session.role)
+            c.delegateClass = CarPlayScene.self
+            return c
+        }
+        return UISceneConfiguration(name: "Phone", sessionRole: session.role)
+    }
+
+    /// Siri: "Play <album> on Stemify".
+    func application(_ application: UIApplication, handlerFor intent: INIntent) -> Any? {
+        intent is INPlayMediaIntent ? PlayMediaHandler() : nil
+    }
+}
+
+@main
+struct StemifyApp: App {
+    @UIApplicationDelegateAdaptor(AppDelegate.self) private var delegate
+    @Environment(\.scenePhase) private var phase
+
+    var body: some Scene {
+        WindowGroup {
+            RootView()
+        }
+        .onChange(of: phase) { _, p in
+            if p == .active { AppGraph.shared.eq.refreshRoute() }
+        }
+    }
+}