UI/UX improvements for the "add a price for a product without barcode" page

The current implementation of PriceCategoryInputPage should be improved:

• for UI consistency reasons, it should use SmoothCardWithRoundedHeader
• for UX reasons, it should be possible to "clear" the category and to remove "origin" items one by one (something like a "delete" icon at the end of the "read-only" lines)
• and probably other UI/UX improvements.
• [Edit] We also need to add an optional multivalue field for "labels"

| current version | with Smooth Card With Rounded Header | | -- | -- | | | |