feat(ios): port the Android client to SwiftUI

The iOS client is now a screen-for-screen port of the Android app over the
same pstr-android UniFFI surface, with no Rust changes: Library, title page,
History, Shares (public links and Drive folders), Downloads and Settings,
with the same strings, undo snackbars and two-pane layout on wide screens.

- Theme from the engine's palette (Material role names, Inter, the same
  type ramp and corners), repainted live from the appearance settings.
- Account sign-in with two-factor code, mailbox password and the Proton
  CAPTCHA in a non-persistent WKWebView, the Drive folder browser, and
  watch-history sync every five minutes, after sign-in, on player close and
  when the app leaves the screen.
- Player over libmpv: resume, progress saved every 5 s, autoplay with the
  up-next card, skip and auto-skip from the chapter plan, track, speed,
  volume and episode pickers, landscape lock, mini transport, and
  lock-screen controls with interruption and route-change handling.
- Offline downloads with the Android record format, free-space floor,
  retries, transfer rate and the Wi-Fi-only policy; interrupted transfers
  resume at next launch.
- Config, data and download state are excluded from backup, as Android's
  allowBackup=false: a restore would bring shares back without their
  Keychain secrets and give two devices one sync identity.

Picture-in-picture, the share sheet and background downloads are not
possible the same way on iOS; docs/IOS.md lists why and what replaces them.

Adds XCTest ports of the Android unit tests, a `test` command to
scripts/build-ios.sh, the app icon and its render script, and an iOS
workflow on macos-15 that runs the tests and builds the unsigned .ipa.

ios/ProtonStream/App/ProtonStreamApp.swift

@@ -1,48 +1,338 @@
 import AVFoundation
 import SwiftUI
+import UIKit
 
 @main
 struct ProtonStreamApp: App {
+    @UIApplicationDelegateAdaptor(AppDelegate.self) private var delegate
     @State private var model = AppModel()
+    @State private var appearance = AppearanceState.shared
 
     init() {
         // `.playback` keeps the audio going with the screen locked or the app
         // in the background, which `UIBackgroundModes: audio` then permits.
         try? AVAudioSession.sharedInstance().setCategory(.playback, mode: .moviePlayback)
+        // The palette read before the first frame, so the first frame is
+        // already painted in it.
+        AppearanceState.shared.seed(NativeRuntime.initialPalette())
     }
 
     var body: some Scene {
         WindowGroup {
+            let scheme = appearance.scheme
             RootView()
                 .environment(model)
-                .preferredColorScheme(.dark)
+                .environment(\.scheme, scheme)
+                .preferredColorScheme(scheme.colorScheme)
+                .tint(scheme.primary)
+                .font(.inter(.bodyLarge))
+                .background(scheme.background.ignoresSafeArea())
+                .task { await appearance.load() }
+        }
+    }
+}
+
+final class AppDelegate: NSObject, UIApplicationDelegate {
+    func application(_: UIApplication, supportedInterfaceOrientationsFor _: UIWindow?) -> UIInterfaceOrientationMask {
+        MainActor.assumeIsolated { OrientationLock.mask }
+    }
+}
+
+/// From this width the library and an open title share the window.
+private let twoPaneWidth: CGFloat = 840
+
+/// From this width the destinations are a rail down the side, not a bar.
+private let railWidth: CGFloat = 600
+
+/// How much room the floating mini transport needs at the foot of a page.
+private let miniTransportInset: CGFloat = 88
+
+enum Destination: String, CaseIterable {
+    case library, history, shares, downloads, settings
+
+    var label: String {
+        switch self {
+        case .library: "Library"
+        case .history: "History"
+        case .shares: "Shares"
+        case .downloads: "Downloads"
+        case .settings: "Settings"
+        }
+    }
+
+    var icon: String {
+        switch self {
+        case .library: "play.rectangle.on.rectangle.fill"
+        case .history: "clock.arrow.circlepath"
+        case .shares: "square.and.arrow.up"
+        case .downloads: "arrow.down.circle"
+        case .settings: "gearshape"
         }
     }
 }
 
 struct RootView: View {
     @Environment(AppModel.self) private var model
+    @Environment(\.scheme) private var scheme
+    @Environment(\.scenePhase) private var phase
+    // Keys, not records: what has to survive is *which* title, and a record is
+    // no longer current after the library reloads. Everything else is derived,
+    // so a reload that renames a season updates the open screen.
+    @SceneStorage("destination") private var destination: Destination = .library
+    @SceneStorage("selectedTitle") private var selectedTitleKey: String?
+    @State private var incomingLink: String?
+    @State private var host = PlayerHost.shared
 
     var body: some View {
-        if let failure = model.startupError {
-            ContentUnavailableView("Could not start", systemImage: "exclamationmark.triangle", description: Text(failure))
-        } else {
-            TabView {
-                NavigationStack { LibraryView() }
-                    .tabItem { Label("Library", systemImage: "play.rectangle.on.rectangle") }
-                NavigationStack { SharesView() }
-                    .tabItem { Label("Shares", systemImage: "link") }
-                NavigationStack { SettingsView() }
-                    .tabItem { Label("Settings", systemImage: "gearshape") }
+        GeometryReader { geometry in
+            let wide = geometry.size.width >= railWidth
+            ZStack(alignment: .bottom) {
+                HStack(spacing: 0) {
+                    if wide { NavigationRail(destination: $destination, onSelect: select) }
+                    page(width: geometry.size.width)
+                        .safeAreaInset(edge: .bottom, spacing: 0) {
+                            VStack(spacing: 8) {
+                                if host.isOpen && host.minimized {
+                                    MiniTransport(host: host)
+                                }
+                                if !wide { NavigationBar(destination: $destination, onSelect: select) }
+                            }
+                        }
+                }
+                Snackbar()
+                    .padding(.bottom, (wide ? 16 : 72) + (host.isOpen && host.minimized ? miniTransportInset : 0))
             }
-            .task { await model.reload() }
-            .alert("Something went wrong", isPresented: .init(
-                get: { model.error != nil },
-                set: { if !$0 { model.error = nil } }
-            )) {
-                Button("OK", role: .cancel) {}
-            } message: {
-                Text(model.error ?? "")
+            .background(scheme.background.ignoresSafeArea())
+        }
+        .overlay {
+            // Over the shell rather than instead of it: the page behind stays
+            // where it was, so leaving the player finds the title page as it was.
+            if host.isOpen && !host.minimized {
+                Group {
+                    if let player = host.player {
+                        PlayerView(host: host, player: player)
+                    } else {
+                        ZStack(alignment: .topTrailing) {
+                            Color.black.ignoresSafeArea()
+                            Text(host.playbackError ?? "Playback is unavailable: libmpv did not start.")
+                                .foregroundStyle(.white)
+                                .frame(maxWidth: .infinity, maxHeight: .infinity)
+                            IconButton("xmark", "Close", tint: .white, action: host.close)
+                        }
+                    }
+                }
+                .transition(.move(edge: .bottom))
+            }
+        }
+        .animation(.easeInOut(duration: 0.25), value: host.isOpen && !host.minimized)
+        .onAppear {
+            model.start()
+            host.onSaveProgress = { [model] episode, position, duration, watched in
+                model.saveProgress(episode, position: position, duration: duration, watched: watched)
+            }
+            host.onClosed = { [model] in model.playerClosed() }
+        }
+        .onChange(of: model.titles) { _, titles in host.update(titles: titles) }
+        .onChange(of: phase) { _, phase in
+            switch phase {
+            case .background:
+                host.enteredBackground()
+                model.syncInBackground()
+            case .active:
+                host.enteredForeground()
+                DownloadCoordinator.shared.resumeQueued()
+            default:
+                break
+            }
+        }
+        // A link opened in this app: show the Add form with it filled in. A
+        // playing episode keeps going in the mini transport rather than
+        // covering the form.
+        .onOpenURL { url in
+            guard let link = shareLink(from: url) else { return }
+            incomingLink = link
+            destination = .shares
+            selectedTitleKey = nil
+            if host.isOpen { host.minimized = true }
+        }
+    }
+
+    private func select(_ target: Destination) {
+        destination = target
+        selectedTitleKey = nil
+    }
+
+    private func play(_ title: TitleRecord, _ index: Int) {
+        host.play(title, at: index)
+    }
+
+    @ViewBuilder private func page(width: CGFloat) -> some View {
+        switch destination {
+        case .library:
+            libraryPage(width: width)
+        case .history:
+            HistoryView(onPlay: play, onTitle: { title in
+                destination = .library
+                selectedTitleKey = title.key
+            })
+        case .shares:
+            SharesView(incomingLink: $incomingLink)
+        case .downloads:
+            DownloadsView()
+        case .settings:
+            SettingsView()
+        }
+    }
+
+    /// Side by side where there is room for both: on a tablet the library
+    /// stays in view while a title is open, so moving between titles is one
+    /// tap rather than back and in again.
+    @ViewBuilder private func libraryPage(width: CGFloat) -> some View {
+        let selected = selectedTitleKey.flatMap { key in model.titles.first { $0.key == key } }
+        let library = LibraryView(onResume: play, onTitle: { title in withAnimation(.easeOut(duration: 0.25)) { selectedTitleKey = title.key } })
+        if width >= twoPaneWidth {
+            HStack(spacing: 0) {
+                library.frame(width: width * 0.45)
+                Rectangle().fill(scheme.outlineVariant).frame(width: 1).ignoresSafeArea()
+                Group {
+                    if let selected { titlePane(selected) } else { EmptyState("Choose a title", "Its seasons and episodes open here.") }
+                }
+                .frame(maxWidth: .infinity)
+            }
+        } else {
+            // The library stays underneath the title page rather than being
+            // rebuilt, so going back finds the grid scrolled where it was.
+            ZStack {
+                library
+                    .opacity(selected == nil ? 1 : 0)
+                    .allowsHitTesting(selected == nil)
+                    .accessibilityHidden(selected != nil)
+                if let selected {
+                    titlePane(selected)
+                        .transition(.asymmetric(insertion: .move(edge: .trailing), removal: .opacity.combined(with: .scale(scale: 0.9))))
+                        .zIndex(1)
+                }
+            }
+        }
+    }
+
+    private func titlePane(_ selected: TitleRecord) -> some View {
+        TitleView(
+            title: selected,
+            onPlay: { _, index in host.play(selected, at: index) },
+            onBack: { withAnimation(.easeOut(duration: 0.25)) { selectedTitleKey = nil } },
+            franchise: selected.franchise.compactMap { key in model.titles.first { $0.key == key } },
+            onOpenTitle: { selectedTitleKey = $0.key }
+        )
+        .id(selected.key)
+    }
+}
+
+/// The destinations along the foot of a phone, the selected one in an accent
+/// pill — the desktop's rule is that the accent marks the thing you are on.
+private struct NavigationBar: View {
+    @Binding var destination: Destination
+    let onSelect: (Destination) -> Void
+    @Environment(\.scheme) private var scheme
+
+    var body: some View {
+        HStack(spacing: 0) {
+            ForEach(Destination.allCases, id: \.self) { item in
+                let selected = item == destination
+                Button { onSelect(item) } label: {
+                    VStack(spacing: 4) {
+                        Image(systemName: item.icon)
+                            .font(.system(size: 18))
+                            .foregroundStyle(selected ? scheme.onPrimary : scheme.onSurfaceVariant)
+                            .frame(width: 56, height: 30)
+                            .background(selected ? scheme.primary : .clear, in: Capsule())
+                        Text(item.label)
+                            .textStyle(.labelMedium, semibold: selected)
+                            .foregroundStyle(selected ? scheme.onSurface : scheme.onSurfaceVariant)
+                            .lineLimit(1)
+                            .minimumScaleFactor(0.8)
+                    }
+                    .frame(maxWidth: .infinity)
+                    .padding(.top, 10)
+                    .padding(.bottom, 6)
+                    .contentShape(Rectangle())
+                }
+                .buttonStyle(.plain)
+                .accessibilityLabel(item.label)
+                .accessibilityAddTraits(selected ? .isSelected : [])
+            }
+        }
+        .background(scheme.surfaceContainer.ignoresSafeArea(edges: .bottom))
+    }
+}
+
+/// The same destinations down the side of a wide window.
+private struct NavigationRail: View {
+    @Binding var destination: Destination
+    let onSelect: (Destination) -> Void
+    @Environment(\.scheme) private var scheme
+
+    var body: some View {
+        VStack(spacing: 12) {
+            ForEach(Destination.allCases, id: \.self) { item in
+                let selected = item == destination
+                Button { onSelect(item) } label: {
+                    VStack(spacing: 4) {
+                        Image(systemName: item.icon)
+                            .font(.system(size: 18))
+                            .foregroundStyle(selected ? scheme.onPrimary : scheme.onSurfaceVariant)
+                            .frame(width: 56, height: 32)
+                            .background(selected ? scheme.primary : .clear, in: Capsule())
+                        Text(item.label)
+                            .textStyle(.labelMedium, semibold: selected)
+                            .foregroundStyle(selected ? scheme.onSurface : scheme.onSurfaceVariant)
+                    }
+                    .frame(width: 80)
+                    .contentShape(Rectangle())
+                }
+                .buttonStyle(.plain)
+                .accessibilityLabel(item.label)
+                .accessibilityAddTraits(selected ? .isSelected : [])
+            }
+            Spacer()
+        }
+        .padding(.top, 24)
+        .background(scheme.surface.ignoresSafeArea())
+    }
+}
+
+/// The app's one line of feedback: what just happened, with Undo where it can
+/// be taken back.
+private struct Snackbar: View {
+    @Environment(AppModel.self) private var model
+    @Environment(\.scheme) private var scheme
+
+    var body: some View {
+        if let message = model.message {
+            HStack(spacing: 8) {
+                Text(message)
+                    .textStyle(.bodyMedium)
+                    .foregroundStyle(scheme.inverseOnSurface)
+                    .frame(maxWidth: .infinity, alignment: .leading)
+                if model.undo != nil {
+                    Button("Undo", action: model.performUndo)
+                        .textStyle(.labelLarge)
+                        .foregroundStyle(scheme.inversePrimary)
+                        .buttonStyle(.plain)
+                        .padding(.horizontal, 8)
+                }
+            }
+            .padding(.horizontal, 16)
+            .padding(.vertical, 14)
+            .background(scheme.inverseSurface, in: RoundedRectangle(cornerRadius: Corner.tight))
+            .padding(.horizontal, 12)
+            .transition(.move(edge: .bottom).combined(with: .opacity))
+            .onTapGesture(perform: model.dismissMessage)
+            // Long with an Undo to reach for, short without — Material's two
+            // snackbar durations.
+            .task(id: message) {
+                try? await Task.sleep(for: .seconds(model.undo != nil ? 10 : 4))
+                if !Task.isCancelled, model.message == message { model.dismissMessage() }
             }
         }
     }