use real photos instead of mocked ones

[leotschritter]

At the moment of the issue creation the photos for the OCR'red and normal PDF saving are mocked photos. TODO:

• [x] pass them from the camera
• [x] show actual last image in the scan_box_last_image.dart
• [x] show the actual count of the images in the scan_box_last_image.dart
• [x] pass them from the crop service after editing them