Cupertino gallery app (#2715)

Resolves #2519 

Part of the larger effort to bring the samples/repo into a stable and
maintainable condition that _also_ remains useful. See: #2409

## 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 have added sample code updates to the [changelog].
- [x] I updated/added relevant documentation (doc comments with `///`).

cupertino_gallery/lib/gallery_home.dart

@@ -0,0 +1,52 @@
+import 'package:flutter/cupertino.dart';
+import 'settings_page.dart';
+import 'widgets_page.dart';
+
+class GalleryHome extends StatelessWidget {
+  const GalleryHome({
+    super.key,
+    required this.onThemeChange,
+    required this.isDarkMode,
+    required this.onTextSizeChange,
+    required this.textSize,
+  });
+
+  final ValueChanged<bool> onThemeChange;
+  final bool isDarkMode;
+  final ValueChanged<double> onTextSizeChange;
+  final double textSize;
+
+  @override
+  Widget build(BuildContext context) {
+    return CupertinoTabScaffold(
+      tabBar: CupertinoTabBar(
+        items: const <BottomNavigationBarItem>[
+          BottomNavigationBarItem(
+            icon: Icon(CupertinoIcons.list_bullet),
+            label: 'Widgets',
+          ),
+          BottomNavigationBarItem(
+            icon: Icon(CupertinoIcons.settings),
+            label: 'Settings',
+          ),
+        ],
+      ),
+      tabBuilder: (BuildContext context, int index) {
+        return CupertinoTabView(
+          builder: (BuildContext context) {
+            return switch (index) {
+              0 => const WidgetsPage(),
+              1 => SettingsPage(
+                    onThemeChange: onThemeChange,
+                    isDarkMode: isDarkMode,
+                    onTextSizeChange: onTextSizeChange,
+                    textSize: textSize,
+                  ),
+              _ => const Center(child: Text('Widgets')),
+            };
+          },
+        );
+      },
+    );
+  }
+}