fix: replace deprecated NavigationView with NavigationStack in SettingsView

Sources/App/AppState.swift

@@ -7,6 +7,8 @@ final class AppState: ObservableObject {
     static let shared = AppState()
 
     @Published var credential: SidecarCredential? = nil
+    @Published var isLocked = false
+    @Published var lastForegroundedAt: Date = Date()
 
     private init() {
         // Try loading persisted credential on launch
@@ -22,4 +24,18 @@ final class AppState: ObservableObject {
         credential = nil
         Keychain.shared.delete(key: "piremote.credential")
     }
+
+    // MARK: - Face ID gate
+
+    func appDidBackground() {
+        lastForegroundedAt = Date()
+    }
+
+    func appWillForeground() async {
+        let elapsed = Date().timeIntervalSince(lastForegroundedAt)
+        guard elapsed > 60 else { return }  // within 60s → no re-auth
+        isLocked = true
+        let ok = await FaceIDGate.authenticate()
+        isLocked = !ok
+    }
 }

Sources/App/ContentView.swift

@@ -4,8 +4,10 @@ import SwiftUI
 
 struct ContentView: View {
     @EnvironmentObject var appState: AppState
+    @Environment(\.scenePhase) private var scenePhase
 
     var body: some View {
+        ZStack {
             Group {
                 if let credential = appState.credential {
                     MainTerminalView(credential: credential)
@@ -15,5 +17,18 @@ struct ContentView: View {
                     }
                 }
             }
+            .onChange(of: scenePhase) { _, new in
+                if new == .background {
+                    appState.appDidBackground()
+                } else if new == .active {
+                    Task { await appState.appWillForeground() }
+                }
+            }
+
+            if appState.isLocked {
+                LockView()
+            }
+        }
+        .task { await appState.appWillForeground() }
     }
 }

Sources/Core/Auth/FaceIDGate.swift

@@ -0,0 +1,24 @@
+// Sources/Core/Auth/FaceIDGate.swift
+// T-2.11: Biometric gate — evaluates Face ID if enabled in settings.
+
+import Foundation
+import LocalAuthentication
+
+/// Evaluates biometrics if Face ID is enabled in settings.
+/// Returns true if auth succeeded or Face ID is disabled.
+struct FaceIDGate: Sendable {
+    @MainActor
+    static func authenticate(reason: String = "Unlock pi remote") async -> Bool {
+        guard UserDefaults.standard.bool(forKey: "faceid.enabled") else { return true }
+        let context = LAContext()
+        var error: NSError?
+        guard context.canEvaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, error: &error) else {
+            return true  // no biometrics available → allow
+        }
+        do {
+            return try await context.evaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, localizedReason: reason)
+        } catch {
+            return false
+        }
+    }
+}

Sources/UI/Settings/LockView.swift

@@ -0,0 +1,16 @@
+// Sources/UI/Settings/LockView.swift
+// T-2.11: Full-screen lock overlay shown when isLocked == true.
+
+import SwiftUI
+
+struct LockView: View {
+    var body: some View {
+        ZStack {
+            Rectangle().fill(.ultraThinMaterial).ignoresSafeArea()
+            VStack(spacing: 16) {
+                Image(systemName: "lock.fill").font(.system(size: 48))
+                Text("Locked").font(.title2)
+            }
+        }
+    }
+}

Sources/UI/Settings/SettingsView.swift

@@ -0,0 +1,48 @@
+// Sources/UI/Settings/SettingsView.swift
+// T-2.11: Settings sheet — Face ID toggle + credential info + unpair.
+
+import LocalAuthentication
+import SwiftUI
+
+@MainActor
+struct SettingsView: View {
+    let credential: SidecarCredential
+    @EnvironmentObject var appState: AppState
+    @Environment(\.dismiss) var dismiss
+
+    @AppStorage("faceid.enabled") private var faceIDEnabled = false
+
+    var body: some View {
+        NavigationStack {
+            Form {
+                Section("Security") {
+                    Toggle("Require Face ID", isOn: $faceIDEnabled)
+                    if faceIDEnabled {
+                        Text("Face ID is required on launch and after 60 seconds in background.")
+                            .font(.caption)
+                            .foregroundStyle(.secondary)
+                    }
+                }
+
+                Section("Sidecar") {
+                    LabeledContent("Name", value: credential.sidecarName)
+                    LabeledContent("Host", value: "\(credential.host):\(credential.port)")
+                    LabeledContent("Paired", value: credential.pairedAt.formatted(date: .abbreviated, time: .shortened))
+                }
+
+                Section("Danger") {
+                    Button("Unpair", role: .destructive) {
+                        appState.unpair()
+                        dismiss()
+                    }
+                }
+            }
+            .navigationTitle("Settings")
+            .toolbar {
+                ToolbarItem(placement: .topBarTrailing) {
+                    Button("Done") { dismiss() }
+                }
+            }
+        }
+    }
+}

Sources/UI/Terminal/MainTerminalView.swift

@@ -13,6 +13,7 @@ struct MainTerminalView: View {
     @State private var connection: SessionConnection? = nil
     @State private var statusText = "Connecting…"
     @State private var cancellables = Set<AnyCancellable>()
+    @State private var showSettings = false
     @EnvironmentObject var appState: AppState
 
     var body: some View {
@@ -23,6 +24,10 @@ struct MainTerminalView: View {
                     .font(.caption.monospaced())
                     .foregroundStyle(.secondary)
                 Spacer()
+                Button { showSettings = true } label: {
+                    Image(systemName: "gear")
+                }
+                .font(.caption)
                 Button("Unpair") {
                     appState.unpair()
                 }
@@ -51,6 +56,9 @@ struct MainTerminalView: View {
             .background(Color(uiColor: .secondarySystemBackground))
         }
         .task { await bootstrap() }
+        .sheet(isPresented: $showSettings) {
+            SettingsView(credential: credential).environmentObject(appState)
+        }
     }
 
     // MARK: - Bootstrap