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/ChannelEditView.swift

@@ -0,0 +1,38 @@
+import SwiftUI
+
+struct ChannelEditView: View {
+    let channelId: UInt32?
+    @Bindable var session: SessionState
+    @Environment(\.dismiss) private var dismiss
+
+    @State private var name = ""
+    @State private var topic = ""
+
+    var body: some View {
+        NavigationStack {
+            Form {
+                Section("Channel Info") {
+                    TextField("Name", text: $name)
+                        .autocorrectionDisabled()
+                        .accessibilityLabel("Channel name")
+                    TextField("Topic (optional)", text: $topic)
+                        .accessibilityLabel("Channel topic, optional")
+                }
+            }
+            .navigationTitle(channelId == nil ? "New Channel" : "Edit Channel")
+            .navigationBarTitleDisplayMode(.inline)
+            .toolbar {
+                ToolbarItem(placement: .cancellationAction) {
+                    Button("Cancel") { dismiss() }
+                }
+                ToolbarItem(placement: .confirmationAction) {
+                    Button("Save") {
+                        session.createChannel(name: name, topic: topic)
+                        dismiss()
+                    }
+                    .disabled(name.trimmingCharacters(in: .whitespaces).isEmpty)
+                }
+            }
+        }
+    }
+}