Cleaning up Veggie Seasons (#2416)

## Pre-launch Checklist

- [x] I read the [Flutter Style Guide] _recently_, and have followed its
advice.
- [x] I signed the [CLA].
- [x] I read the [Contributors Guide].
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] All existing and new tests are passing.

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veggieseasons/lib/widgets/veggie_seasons_page.dart

@@ -0,0 +1,45 @@
+// Copyright 2024, the Flutter project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:flutter/cupertino.dart';
+
+class VeggieSeasonsPage<T> extends Page<T> {
+  final Widget child;
+
+  const VeggieSeasonsPage({
+    super.key,
+    required this.child,
+    super.restorationId,
+  });
+
+  @override
+  VeggieSeasonsPageRoute<T> createRoute(BuildContext context) =>
+      VeggieSeasonsPageRoute<T>(this);
+}
+
+class VeggieSeasonsPageRoute<T> extends PageRoute<T> {
+  VeggieSeasonsPageRoute(VeggieSeasonsPage<T> page) : super(settings: page);
+
+  VeggieSeasonsPage<T> get _page => settings as VeggieSeasonsPage<T>;
+
+  @override
+  Color? get barrierColor => null;
+
+  @override
+  String? get barrierLabel => null;
+
+  @override
+  bool get maintainState => true;
+
+  @override
+  Duration get transitionDuration => Duration.zero;
+
+  @override
+  Widget buildPage(
+    BuildContext context,
+    Animation<double> animation,
+    Animation<double> secondaryAnimation,
+  ) =>
+      _page.child;
+}