feat(ios): ship iOS SwiftUI client (VoiceCatiOS)

Full SwiftUI app at clients/apple/iOS/VoiceCatiOS.xcodeproj:
- 24 Swift source files: AppState + SessionState (@Observable @MainActor),
  AudioSessionManager (AVAudioSession owner + interruption/route handling),
  ServerListStore/SavedServer (App Group container + Keychain sharing),
  and 14 SwiftUI views covering the full feature set
- NavigationSplitView on iPad, TabView on iPhone (horizontalSizeClass)
- Channel tree via OutlineGroup, user list with context menu admin actions
- PTT via DragGesture(minimumDistance: 0) + @GestureState
- onEvent closures hop to MainActor via Task { @MainActor in ... }
- App Group: group.cat.voice.VoiceCat (shared with future ReplayKit extension)

C ABI: add vc_audio_suspend / vc_audio_resume (AudioEngine::suspend/resume)
called by AudioSessionManager on AVAudioSession interruption events.

XCFramework: add ios-arm64 and ios-arm64-simulator slices to build-xcframework.sh;
Package.swift gains .iOS(.v17) platform; CMakePresets.json adds apple-ios /
apple-ios-sim presets with arm64-ios / arm64-ios-simulator vcpkg triplets.

Verified: xcodebuild -target VoiceCatiOS -sdk iphonesimulator26.5 BUILD SUCCEEDED.

CLAUDE.md

@@ -6,9 +6,10 @@ and what's next* read [`PROGRESS.md`](PROGRESS.md); for *design* read [`docs/`](
 
 > **One-line status:** M5 (moderation & admin UI) is complete — permissions, kick/ban/move,
 > server-mute, channel CRUD, in-app account management, disconnect/keepalive/reaper. Windows
-> WinForms C# client is shipped (M4). **macOS AppKit client shipped** — `VoiceCatMac.xcodeproj`
-> at `clients/apple/macOS/`. `ctest --preset dev` green — 21/21 tests.
-> iOS SwiftUI client is next. See [`PROGRESS.md`](PROGRESS.md).
+> WinForms C# client shipped (M4). **macOS AppKit client shipped** — `VoiceCatMac.xcodeproj`
+> at `clients/apple/macOS/`. **iOS SwiftUI client shipped** — `VoiceCatiOS.xcodeproj` at
+> `clients/apple/iOS/`. `ctest --preset dev` green — 21/21 tests.
+> Next: ReplayKit Broadcast Extension or DRED/audio polish. See [`PROGRESS.md`](PROGRESS.md).
 
 VoiceCat = self-hosted native voice & text chat (TeamSpeak/Mumble-style). Plain TCP (control)
 + UDP (media), no WebRTC, encrypted by default. A shared C++ core (`libvoicecat`) drives