Refactor Cart into checkerboard table

Closes: #173 (closed)

Removes clear all feature from: #233

This one improves focus behavior in the cart, moving cart items and deleting items from the cart.

clive/__private/ui/operations/cart.py

@@ -160,9 +160,10 @@ class CartItem(CliveCheckerboardTableRow, CliveWidget):
     def focus(self, _: bool = True) -> Self:  # noqa: FBT001, FBT002
         def focus_first_focusable_button() -> None:
             buttons = self.query(CliveButton)
-            for button in reversed(buttons):
+            for button in buttons:
                 if button.focusable:
                     button.focus()
+                    break
 
         focused = self.app.focused
         if not focused: