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/BanUserView.swift

@@ -0,0 +1,58 @@
+import SwiftUI
+import VoiceCatCore
+
+struct BanUserView: View {
+    let user: User
+    @Bindable var session: SessionState
+    @Environment(\.dismiss) private var dismiss
+
+    @State private var reason = ""
+    @State private var permanent = true
+    @State private var duration: Double = 60  // minutes
+
+    var body: some View {
+        NavigationStack {
+            Form {
+                Section("Ban \(user.nickname)") {
+                    TextField("Reason (optional)", text: $reason)
+                        .accessibilityLabel("Ban reason, optional")
+                    Toggle("Permanent", isOn: $permanent)
+                        .accessibilityLabel("Permanent ban")
+                    if !permanent {
+                        HStack {
+                            Text("Duration")
+                            Slider(value: $duration, in: 1...10080, step: 1)
+                                .accessibilityLabel("Ban duration in minutes")
+                            Text(formattedDuration)
+                                .monospacedDigit()
+                                .frame(width: 60, alignment: .trailing)
+                        }
+                    }
+                }
+            }
+            .navigationTitle("Ban User")
+            .navigationBarTitleDisplayMode(.inline)
+            .toolbar {
+                ToolbarItem(placement: .cancellationAction) {
+                    Button("Cancel") { dismiss() }
+                }
+                ToolbarItem(placement: .confirmationAction) {
+                    Button("Ban", role: .destructive) {
+                        let expiresMs: UInt64 = permanent ? 0
+                            : UInt64(Date().timeIntervalSince1970 * 1000) + UInt64(duration * 60 * 1000)
+                        session.banUser(user.id, reason: reason, expiresUnixMs: expiresMs)
+                        dismiss()
+                    }
+                }
+            }
+        }
+    }
+
+    private var formattedDuration: String {
+        let mins = Int(duration)
+        if mins < 60 { return "\(mins)m" }
+        let hours = mins / 60
+        if hours < 24 { return "\(hours)h" }
+        return "\(hours / 24)d"
+    }
+}