feat(home): add large featured cards for extension feeds

test/explore_featured_section_test.dart

@@ -0,0 +1,91 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:spotiflac_android/providers/explore_provider.dart';
+import 'package:spotiflac_android/widgets/explore_featured_section.dart';
+
+void main() {
+  test('featured layout and artwork survive cache serialization', () {
+    final section = ExploreSection.fromJson({
+      'uri': 'featured',
+      'title': 'New',
+      'layout': 'featured',
+      'items': [
+        {
+          'id': 'collection-1',
+          'type': 'playlist',
+          'name': 'Featured playlist',
+          'cover_url': 'https://example.test/cover.jpg',
+          'featured_cover_url': 'https://example.test/banner.jpg',
+          'heading': 'Updated playlist',
+          'provider_id': 'example-provider',
+        },
+      ],
+    });
+    final restored = ExploreSection.fromJson(section.toJson());
+    expect(restored.isFeatured, isTrue);
+    expect(restored.items.single.heading, 'Updated playlist');
+    expect(restored.items.single.featuredCoverUrl, endsWith('/banner.jpg'));
+    expect(restored.items.single.coverUrl, endsWith('/cover.jpg'));
+    expect(restored.items.single.providerId, 'example-provider');
+    expect(ExploreSection.fromJson({'items': <Object?>[]}).isFeatured, isFalse);
+  });
+
+  for (final (size, scale) in [
+    (const Size(390, 844), 1.0),
+    (const Size(320, 844), 2.0),
+    (const Size(1024, 768), 1.0),
+  ]) {
+    testWidgets('featured cards scroll and open at $size, text scale $scale', (
+      tester,
+    ) async {
+      tester.view.physicalSize = size;
+      tester.view.devicePixelRatio = 1;
+      addTearDown(tester.view.reset);
+      ExploreItem? opened;
+      final items = List.generate(
+        4,
+        (index) => ExploreItem(
+          id: 'collection-$index',
+          uri: 'example:collection:$index',
+          type: 'album',
+          name: 'Featured $index',
+          artists: 'Example artist',
+          heading: 'New album',
+          description: 'An editorial description of the featured album.',
+        ),
+      );
+      await tester.pumpWidget(
+        MaterialApp(
+          home: MediaQuery(
+            data: MediaQueryData(textScaler: TextScaler.linear(scale)),
+            child: Scaffold(
+              body: SingleChildScrollView(
+                child: ExploreFeaturedSection(
+                  section: ExploreSection(
+                    uri: 'featured',
+                    title: 'New',
+                    items: items,
+                    isFeatured: true,
+                  ),
+                  onItemTap: (item) => opened = item,
+                ),
+              ),
+            ),
+          ),
+        ),
+      );
+      expect(tester.takeException(), isNull);
+      final card = find.ancestor(
+        of: find.text('Featured 0'),
+        matching: find.byType(GestureDetector),
+      );
+      expect(tester.getSize(card).width, greaterThan(250));
+      await tester.tap(find.text('Featured 0'));
+      expect(opened?.id, 'collection-0');
+      await tester.drag(find.byType(ListView), const Offset(-600, 0));
+      await tester.pumpAndSettle();
+      expect(find.text('Featured 2'), findsOneWidget);
+      expect(tester.takeException(), isNull);
+    });
+  }
+}