fix: reformat code / code improvements

lib/models/bar_tab.dart

@@ -1,4 +1,5 @@
 import 'tab_item.dart';
+import '../utils/collection_utils.dart';
 
 class BarTab {
   final String id;
@@ -40,7 +41,7 @@ class BarTab {
           status == other.status &&
           openedAt == other.openedAt &&
           closedAt == other.closedAt &&
-          _listEquals(items, other.items);
+          listEquals(items, other.items);
 
   @override
   int get hashCode => Object.hash(
@@ -53,12 +54,4 @@ class BarTab {
       );
 }
 
-bool _listEquals<T>(List<T>? a, List<T>? b) {
-  if (identical(a, b)) return true;
-  if (a == null || b == null) return a == b;
-  if (a.length != b.length) return false;
-  for (int i = 0; i < a.length; i++) {
-    if (a[i] != b[i]) return false;
-  }
-  return true;
-}
+// _listEquals moved to utils/collection_utils.dart

lib/models/closed_tab.dart

@@ -1,16 +1,18 @@
 import 'package:intl/intl.dart';
 
 import 'closed_tab_item.dart';
+import 'payment_method.dart';
+import '../utils/collection_utils.dart';
 
 class ClosedTab {
   final String id;
   final String originalTabId;
   final String customerName;
   final DateTime closedAt;
-  final String paymentMethod;
-  final List<ClosedTabItem> items;
+final PaymentMethod paymentMethod;
 
-  ClosedTab({
+  final List<ClosedTabItem> items;
+  const ClosedTab({
     required this.id,
     required this.originalTabId,
     required this.customerName,
@@ -27,13 +29,7 @@ class ClosedTab {
   String get formattedTotal =>
       NumberFormat.simpleCurrency().format(totalInCents / 100);
 
-  String get formattedPaymentMethod {
-    return switch (paymentMethod) {
-      'cash' => 'Cash',
-      'payconiq' => 'Payconiq',
-      _ => 'Cash',
-    };
-  }
+  String get formattedPaymentMethod => paymentMethod.label;
 
   @override
   bool operator ==(Object other) =>
@@ -44,7 +40,7 @@ class ClosedTab {
           customerName == other.customerName &&
           closedAt == other.closedAt &&
           paymentMethod == other.paymentMethod &&
-          _listEquals(items, other.items);
+          listEquals(items, other.items);
 
   @override
   int get hashCode => Object.hash(
@@ -57,12 +53,4 @@ class ClosedTab {
       );
 }
 
-bool _listEquals<T>(List<T>? a, List<T>? b) {
-  if (identical(a, b)) return true;
-  if (a == null || b == null) return a == b;
-  if (a.length != b.length) return false;
-  for (int i = 0; i < a.length; i++) {
-    if (a[i] != b[i]) return false;
-  }
-  return true;
-}
+// _listEquals moved to utils/collection_utils.dart

lib/models/payment_method.dart

@@ -0,0 +1,15 @@
+enum PaymentMethod {
+  cash('cash', 'Cash', 'Cash payment'),
+  payconiq('payconiq', 'Payconiq', 'Payconiq QR payment');
+
+  final String value;
+  final String label;
+  final String description;
+
+  const PaymentMethod(this.value, this.label, this.description);
+
+  static PaymentMethod fromValue(String value) => PaymentMethod.values.firstWhere(
+        (e) => e.value == value,
+        orElse: () => PaymentMethod.cash,
+      );
+}