fixes before build

lib/models/line_item.dart

@@ -22,6 +22,14 @@ class LineItem {
   /// Negative amount when a discount was folded into [price].
   final double discount;
 
+  bool get hasDiscount => discount != 0;
+
+  /// List price before a folded discount. Equals [price] when there is none.
+  double get originalPrice {
+    if (!hasDiscount) return price;
+    return ((price - discount) * 100).round() / 100;
+  }
+
   LineItem copyWith({
     String? id,
     String? name,