feat: add equality operators, make history screen paginated, random performance updates

lib/models/bar_tab.dart

@@ -30,4 +30,35 @@ class BarTab {
   }
 
   bool get isOpen => status == 'open';
+
+  @override
+  bool operator ==(Object other) =>
+      identical(this, other) ||
+      other is BarTab &&
+          id == other.id &&
+          customerName == other.customerName &&
+          status == other.status &&
+          openedAt == other.openedAt &&
+          closedAt == other.closedAt &&
+          _listEquals(items, other.items);
+
+  @override
+  int get hashCode => Object.hash(
+        id,
+        customerName,
+        status,
+        openedAt,
+        closedAt,
+        Object.hashAll(items),
+      );
+}
+
+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;
 }