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.

clients/apple/iOS/VoiceCatiOS/Views/VoiceControlsView.swift

@@ -0,0 +1,130 @@
+import SwiftUI
+import VoiceCatCore
+
+struct VoiceControlsView: View {
+    @Bindable var session: SessionState
+
+    var body: some View {
+        HStack(spacing: 20) {
+            // Mic toggle / PTT button
+            if session.voiceState.inputMode == .pushToTalk {
+                PTTButton(session: session)
+            } else {
+                Button {
+                    if session.voiceState.micActive {
+                        session.stopMicStream()
+                    } else {
+                        session.startMicStream()
+                    }
+                } label: {
+                    Image(systemName: session.voiceState.micActive ? "mic.fill" : "mic.slash.fill")
+                        .font(.title2)
+                        .frame(width: 44, height: 44)
+                        .background(session.voiceState.micActive ? Color.green : Color(.systemGray4), in: Circle())
+                        .foregroundStyle(session.voiceState.micActive ? .white : .primary)
+                }
+                .disabled(session.currentChannelId == 0)
+                .accessibilityLabel(session.voiceState.micActive ? "Stop microphone" : "Start microphone")
+            }
+
+            // Level meter
+            LevelMeterView(level: session.voiceState.level)
+                .frame(width: 80, height: 8)
+                .accessibilityHidden(true)
+
+            Spacer()
+
+            // Self mute
+            Button {
+                session.setMute(!session.voiceState.selfMuted, deafened: session.voiceState.selfDeafened)
+            } label: {
+                Image(systemName: session.voiceState.selfMuted ? "mic.slash" : "mic")
+                    .font(.title3)
+                    .foregroundStyle(session.voiceState.selfMuted ? .red : .primary)
+            }
+            .accessibilityLabel(session.voiceState.selfMuted ? "Unmute microphone" : "Mute microphone")
+
+            // Self deafen
+            Button {
+                session.setMute(session.voiceState.selfMuted, deafened: !session.voiceState.selfDeafened)
+            } label: {
+                Image(systemName: session.voiceState.selfDeafened ? "headphones.slash" : "headphones")
+                    .font(.title3)
+                    .foregroundStyle(session.voiceState.selfDeafened ? .red : .primary)
+            }
+            .accessibilityLabel(session.voiceState.selfDeafened ? "Undeafen" : "Deafen")
+
+            // Disconnect
+            Button(role: .destructive) {
+                session.stopMicStream()
+                session.client.disconnect()
+            } label: {
+                Image(systemName: "phone.down.fill")
+                    .font(.title3)
+                    .foregroundStyle(.red)
+            }
+            .accessibilityLabel("Disconnect from server")
+        }
+        .padding(.horizontal, 16)
+        .padding(.vertical, 10)
+        .background(.bar)
+    }
+}
+
+// MARK: - PTT Button (DragGesture instead of NSEvent on iOS)
+
+private struct PTTButton: View {
+    @Bindable var session: SessionState
+    @GestureState private var isPressing = false
+
+    var body: some View {
+        Circle()
+            .fill(isPressing ? Color.blue : Color(.systemGray4))
+            .frame(width: 44, height: 44)
+            .overlay {
+                Image(systemName: "mic.fill")
+                    .foregroundStyle(isPressing ? .white : .primary)
+            }
+            .gesture(
+                DragGesture(minimumDistance: 0)
+                    .updating($isPressing) { _, state, _ in state = true }
+                    .onChanged { _ in
+                        if !isPressing { return }
+                        if !session.voiceState.micActive { session.startMicStream() }
+                        session.setPushToTalk(true)
+                        UIImpactFeedbackGenerator(style: .medium).impactOccurred()
+                    }
+                    .onEnded { _ in
+                        session.setPushToTalk(false)
+                        session.stopMicStream()
+                    }
+            )
+            .accessibilityLabel("Push to talk, hold to transmit")
+            .accessibilityAddTraits(.isButton)
+    }
+}
+
+// MARK: - Level Meter
+
+private struct LevelMeterView: View {
+    let level: Float
+
+    var body: some View {
+        GeometryReader { geo in
+            ZStack(alignment: .leading) {
+                RoundedRectangle(cornerRadius: 4)
+                    .fill(Color(.systemGray5))
+                RoundedRectangle(cornerRadius: 4)
+                    .fill(levelColor)
+                    .frame(width: geo.size.width * CGFloat(min(level * 10, 1.0)))
+                    .animation(.linear(duration: 0.05), value: level)
+            }
+        }
+    }
+
+    private var levelColor: Color {
+        if level > 0.15 { return .orange }
+        if level > 0.05 { return .green }
+        return .green.opacity(0.5)
+    }
+}