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/AccountsView.swift

@@ -0,0 +1,153 @@
+import SwiftUI
+import VoiceCatCore
+
+struct AccountsView: View {
+    @Bindable var session: SessionState
+    @State private var showCreateAccount = false
+    @State private var newUsername = ""
+    @State private var newPassword = ""
+    @State private var accountToDelete: Account?
+    @State private var showResetPassword = false
+    @State private var resetForAccount: Account?
+    @State private var resetPassword = ""
+
+    var body: some View {
+        List {
+            ForEach(session.accounts, id: \.username) { account in
+                AccountRowView(account: account)
+                    .swipeActions(edge: .trailing) {
+                        Button(role: .destructive) {
+                            accountToDelete = account
+                        } label: {
+                            Label("Delete", systemImage: "trash")
+                        }
+                        Button {
+                            resetForAccount = account
+                            showResetPassword = true
+                        } label: {
+                            Label("Reset PW", systemImage: "key")
+                        }
+                        .tint(.orange)
+                    }
+            }
+        }
+        .navigationTitle("Accounts")
+        .navigationBarTitleDisplayMode(.inline)
+        .toolbar {
+            ToolbarItem(placement: .primaryAction) {
+                Button {
+                    showCreateAccount = true
+                } label: {
+                    Image(systemName: "plus")
+                }
+                .accessibilityLabel("Create account")
+            }
+        }
+        .refreshable {
+            session.fetchAccountList()
+        }
+        .onAppear {
+            session.fetchAccountList()
+        }
+        .confirmationDialog("Delete account?", isPresented: Binding(
+            get: { accountToDelete != nil },
+            set: { if !$0 { accountToDelete = nil } }
+        )) {
+            if let a = accountToDelete {
+                Button("Delete \(a.username)", role: .destructive) {
+                    session.deleteAccount(username: a.username)
+                    accountToDelete = nil
+                }
+            }
+            Button("Cancel", role: .cancel) { accountToDelete = nil }
+        }
+        .sheet(isPresented: $showCreateAccount) {
+            CreateAccountSheet(session: session)
+        }
+        .alert("Reset Password", isPresented: $showResetPassword) {
+            SecureField("New password", text: $resetPassword)
+                .accessibilityLabel("New password for account")
+            Button("Reset") {
+                if let a = resetForAccount, !resetPassword.isEmpty {
+                    session.resetPassword(username: a.username, newPassword: resetPassword)
+                }
+                resetPassword = ""
+                resetForAccount = nil
+            }
+            Button("Cancel", role: .cancel) {
+                resetPassword = ""
+                resetForAccount = nil
+            }
+        } message: {
+            Text("Enter a new password for \(resetForAccount?.username ?? "").")
+        }
+    }
+}
+
+private struct AccountRowView: View {
+    let account: Account
+
+    private var joinedDate: String {
+        let date = Date(timeIntervalSince1970: Double(account.createdAtUnixMs) / 1000)
+        return date.formatted(.dateTime.year().month().day())
+    }
+
+    var body: some View {
+        VStack(alignment: .leading, spacing: 2) {
+            HStack {
+                Text(account.username)
+                    .fontWeight(.medium)
+                if account.isAdmin {
+                    Text("admin")
+                        .font(.caption2)
+                        .padding(.horizontal, 6).padding(.vertical, 2)
+                        .background(.orange.opacity(0.2), in: Capsule())
+                        .foregroundStyle(.orange)
+                }
+            }
+            Text("Created \(joinedDate)")
+                .font(.caption)
+                .foregroundStyle(.secondary)
+        }
+        .accessibilityElement(children: .combine)
+        .accessibilityLabel("\(account.username)\(account.isAdmin ? ", administrator" : ""), created \(joinedDate)")
+    }
+}
+
+private struct CreateAccountSheet: View {
+    @Bindable var session: SessionState
+    @Environment(\.dismiss) private var dismiss
+    @State private var username = ""
+    @State private var password = ""
+
+    var body: some View {
+        NavigationStack {
+            Form {
+                Section {
+                    TextField("Username", text: $username)
+                        .textContentType(.username)
+                        .autocorrectionDisabled()
+                        .textInputAutocapitalization(.never)
+                        .accessibilityLabel("Username")
+                    SecureField("Password", text: $password)
+                        .textContentType(.newPassword)
+                        .accessibilityLabel("Password")
+                }
+            }
+            .navigationTitle("Create Account")
+            .navigationBarTitleDisplayMode(.inline)
+            .toolbar {
+                ToolbarItem(placement: .cancellationAction) {
+                    Button("Cancel") { dismiss() }
+                }
+                ToolbarItem(placement: .confirmationAction) {
+                    Button("Create") {
+                        session.createAccount(username: username, password: password)
+                        dismiss()
+                    }
+                    .disabled(username.isEmpty || password.isEmpty)
+                }
+            }
+        }
+    }
+}