refactor(terminal): decouple scanner via IFingerprintScanner factory and fix test cancellation token

apps/KronaStaffTerminal.Tests/ScannerRecoveryTests.cs

@@ -88,7 +88,7 @@ public class ScannerRecoveryTests
             int retries = 0;
             while (retries < 5)
             {
-                await Task.Delay(10);
+                await Task.Delay(10, TestContext.Current.CancellationToken);
                 try
                 {
                     scanner.Connect(0, Array.Empty<(int, string)>());
@@ -106,7 +106,7 @@ public class ScannerRecoveryTests
 
         scanner.SimulateDisconnect();
         // Emulate the hardware coming back after a short delay
-        await Task.Delay(20);
+        await Task.Delay(20, TestContext.Current.CancellationToken);
         scanner.AddVirtualDevice(0, "SLK20R", "SERIAL"); // ensure device is discoverable if it was cleared
 
         await reconnectTcs.Task;

apps/KronaStaffTerminal/MainPage.xaml.cs

@@ -17,8 +17,12 @@ public sealed partial class MainPage : Page
     private readonly AttendanceSyncService _attendanceSync = new();
     private readonly AttendanceTracker _attendanceTracker = new();
     private readonly TerminalIpcClient _ipcClient = new();
-    private readonly FingerprintScanner _scanner = new();
+    private readonly IFingerprintScanner _scanner;
     private readonly IUpdateSource _updateSource = new ForgejoUpdateSource();
+
+    /// <summary>Инъекция фабрики для тестирования. По умолчанию создаёт реальный FingerprintScanner.</summary>
+    public static Func<IFingerprintScanner>? ScannerFactory { get; set; }
+
     private TerminalState _state = new();
     private bool _loaded;
     private TaskCompletionSource<bool>? _adminAuthCompletion;
@@ -57,6 +61,8 @@ public sealed partial class MainPage : Page
             CrashLogService.Write(exception);
             throw;
         }
+
+        _scanner = ScannerFactory?.Invoke() ?? new FingerprintScanner();
         _scanner.StatusChanged += message => Enqueue(() => SetStatus(message));
         _scanner.StateChanged += (state, message) => Enqueue(() => HandleScannerStateChanged(state, message));
         _scanner.RegistrationProgress += count => Enqueue(() => SetStatus($"Мастер регистрации: принят скан {count}/3. Уберите палец и приложите снова."));