feat: add panel and device styles to screenshot

[bombsimon]

• --style panel draws glowing LEDs in a housing on a transparent background, --style device the 3D mockup cropped to the device
• Both render through the web page in headless Chrome so they match the live view, Playwright is an optional screenshot extra
• pixels stays the default

Example new screenshot

matrixbox screenshot \
  /path/to/matrixbox/apps/departures \
  --settings /path/to/some-settings.txt \
  --rename settings.txt \
  -o screenshot.png \
  --style device \
  --after-frames 500 \
  --gamma 5.0 \
  --refresh-fps 1000