feat: implement portion control for products in POS system

- Added portion choices functionality to allow products to be sold in fractional quantities.
- Updated KdsOrderPresenter to handle new print URL generation with absolute option.
- Enhanced CSS for portion picker UI and added accessibility features.
- Modified JavaScript to manage portion selection and integrate with the cart system.
- Created new Blade view for portion picker dialog.
- Updated invoice print options to ensure consistent routing.
- Added tests for portion functionality and POS rendering.
