feat(apple): iOS/iPadOS client — touch, pointer lock, shared SwiftUI shell

The whole client now runs on iPadOS/iOS from the same sources, first-lit live in the
iPad simulator against the real host at 1280x720@60 (60 fps on the HUD, capture state
machine active, mic permission flow shown).

- PunktfunkCore.xcframework grows iOS device + universal-simulator slices
  (BUILD_IOS=1; rustup targets aarch64-apple-ios{,-sim} + x86_64-apple-ios).
- The decode pump is extracted into a shared StreamPump (identical IDR re-gate logic on
  both platforms); the iOS StreamView (StreamViewIOS.swift) has the same name/signature
  as the macOS one, so ContentView & co. are byte-identical across platforms — hosted
  in a UIViewController for prefersPointerLocked (the iPadOS cursor capture; see README
  note 9 for the UIHostingController forwarding caveat).
- Touch is always forwarded: per-finger wire ids, coordinates mapped through the
  aspect-fit letterbox into LIVE host-mode pixels (surface == host mode, identity
  rescale host-side; follows mid-stream requestMode switches).
- InputCapture is cross-platform: GC works the same on iPadOS, ⌘⎋ is detected from the
  HID stream there; stale-⌘ tracking after focus loss fixed on both platforms
  (releaseAll now drops the modifier/latch state — a ⌘ released in another app
  otherwise hijacked Esc forever).
- SessionAudio: AVAudioSession on iOS (.playAndRecord + .defaultToSpeaker — without it
  iPhones route host audio to the EARPIECE; deactivated with
  notifyOthersOnDeactivation on stop so interrupted background audio resumes); HAL
  device pinning + the Settings pickers stay macOS-only.
- New Punktfunk-iOS app target (shared synchronized sources, generated Info.plist with
  mic + local-network usage descriptions — QUIC to a LAN host trips local network
  privacy on real devices — scene manifest + indirect input events for Stage Manager /
  external displays), shared scheme, macOS min-window frames gated off iOS.

For the iPad-on-an-external-screen idea: with multiple scenes + indirect input enabled,
Stage Manager iPads can drag the punktfunk window onto the external display and drive
the PC with keyboard/mouse/touch. Known gaps (README note 9): the pointer-lock
preference isn't consulted through UIHostingController (relative mouse works, the local
cursor just stays visible) and AVAudioSession interruptions don't auto-restart audio.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

clients/apple/Sources/PunktfunkClient/PunktfunkClientApp.swift

@@ -1,23 +1,30 @@
 // PunktfunkClient — the macOS client app (also runs unbundled via swift run).
 // Hosts grid → trust-on-first-use → StreamView (AVSampleBufferDisplayLayer HEVC) + input.
 
+#if os(macOS)
 import AppKit
+#endif
 import SwiftUI
 
 @main
 struct PunktfunkClientApp: App {
+    #if os(macOS)
     @NSApplicationDelegateAdaptor(AppDelegate.self) private var appDelegate
+    #endif
 
     var body: some Scene {
         WindowGroup("punktfunk") {
             ContentView()
         }
+        #if os(macOS)
         Settings {
             SettingsView()
         }
+        #endif
     }
 }
 
+#if os(macOS)
 final class AppDelegate: NSObject, NSApplicationDelegate {
     func applicationDidFinishLaunching(_ notification: Notification) {
         // `swift run` launches an unbundled binary; promote it to a regular app so the
@@ -30,3 +37,4 @@ final class AppDelegate: NSObject, NSApplicationDelegate {
         true
     }
 }
+#endif