feat(flutter/home): home screen with five sections

Sections mirror the web home: Recently added · Rediscover (albums +
artists) · Most played · Last played artists. Tap routes pushed for
albums/artists; track-tap is wired in the player task. Pull-to-refresh
re-fetches /api/home.

flutter_client/test/library/home_screen_test.dart

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+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+import 'package:minstrel/library/home_screen.dart';
+import 'package:minstrel/library/library_providers.dart';
+import 'package:minstrel/models/album.dart';
+import 'package:minstrel/models/artist.dart';
+import 'package:minstrel/models/home_data.dart';
+import 'package:minstrel/theme/theme_data.dart';
+
+void main() {
+  testWidgets('home renders sections with rows', (tester) async {
+    final fixture = HomeData(
+      recentlyAddedAlbums: const [
+        AlbumRef(id: 'a', title: 'Geogaddi', artistId: 'x', artistName: 'BoC'),
+      ],
+      rediscoverAlbums: const [],
+      rediscoverArtists: const [
+        ArtistRef(id: 'r', name: 'Aphex Twin'),
+      ],
+      mostPlayedTracks: const [],
+      lastPlayedArtists: const [],
+    );
+    await tester.pumpWidget(ProviderScope(
+      overrides: [
+        homeProvider.overrideWith((ref) async => fixture),
+      ],
+      child: MaterialApp(theme: buildThemeData(), home: const HomeScreen()),
+    ));
+    await tester.pumpAndSettle();
+    expect(find.text('Recently added'), findsOneWidget);
+    expect(find.text('Geogaddi'), findsOneWidget);
+    expect(find.text('Aphex Twin'), findsOneWidget);
+  });
+}