Fix: CameraDevice race condition crash on Android rotation (IllegalStateException)

[Copilot]

Rapid stop/start cycles during device rotation cause a stale OnConfigured() callback to fire after a new CameraDevice has already opened. The callback overwrites previewSession with an old session tied to the already-closed device, then calls SetRepeatingRequest() on it → IllegalStateException: CameraDevice was already closed.

Changes

• Session generation counter — previewSessionGeneration (atomically incremented via Interlocked) is added to MauiCameraView; each StartPreview() invocation captures its own generation value before any await.

• Stale callback detection in OnConfigured() — PreviewCaptureStateCallback now stores the generation at construction time and guards against two stale conditions before touching previewSession:

  if (cameraView.cameraDevice == null ||
      generation != Volatile.Read(ref cameraView.previewSessionGeneration))
  {
      try { session.Close(); } catch (Java.Lang.Exception ex) { DebugOut.WriteLine(ex.ToString()); }
      return;
  }

• Early exit in StartPreview() — after the await Task.Delay loop, bails out if the camera was stopped or a newer StartPreview() ran in the meantime.

• Defensive catch in UpdatePreview() — adds Java.Lang.IllegalStateException alongside the existing CameraAccessException catch as a last-resort safety net.