feat(flutter): MainAppBarActions widget with admin-gated overflow

Shared AppBar actions for top-level screens — three primary icons
(Home/Library/Search, current screen suppressed) plus a kebab containing
Playlists/Discover/Settings and (only when isAdmin) Admin. Replaces the
ad-hoc per-screen IconButton lists; centralises admin-gating logic in
one place so /admin entry can't accidentally leak to non-admins.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

flutter_client/lib/shared/widgets/main_app_bar_actions.dart

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+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:go_router/go_router.dart';
+
+import '../../auth/auth_provider.dart';
+import '../../theme/theme_extension.dart';
+
+/// Shared AppBar `actions` for top-level screens. Renders Home / Library /
+/// Search as primary icons (suppressing the icon for [currentRoute]) plus
+/// a kebab overflow with Playlists / Discover / Settings and (for admins)
+/// Admin.
+class MainAppBarActions extends ConsumerWidget {
+  const MainAppBarActions({super.key, required this.currentRoute});
+
+  final String currentRoute;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final fs = Theme.of(context).extension<FabledSwordTheme>()!;
+    final user = ref.watch(authControllerProvider).valueOrNull;
+    final isAdmin = user?.isAdmin ?? false;
+
+    return Row(
+      mainAxisSize: MainAxisSize.min,
+      children: [
+        if (currentRoute != '/home')
+          IconButton(
+            key: const Key('app_bar_home'),
+            icon: Icon(Icons.home, color: fs.parchment),
+            tooltip: 'Home',
+            onPressed: () => context.go('/home'),
+          ),
+        if (currentRoute != '/library')
+          IconButton(
+            key: const Key('app_bar_library'),
+            icon: Icon(Icons.library_music, color: fs.parchment),
+            tooltip: 'Library',
+            onPressed: () => context.push('/library'),
+          ),
+        if (currentRoute != '/search')
+          IconButton(
+            key: const Key('app_bar_search'),
+            icon: Icon(Icons.search, color: fs.parchment),
+            tooltip: 'Search',
+            onPressed: () => context.push('/search'),
+          ),
+        PopupMenuButton<String>(
+          key: const Key('app_bar_overflow'),
+          icon: Icon(Icons.more_vert, color: fs.parchment),
+          tooltip: 'More',
+          onSelected: (route) => context.push(route),
+          itemBuilder: (_) => [
+            const PopupMenuItem(value: '/playlists', child: Text('Playlists')),
+            const PopupMenuItem(value: '/discover', child: Text('Discover')),
+            const PopupMenuItem(value: '/settings', child: Text('Settings')),
+            if (isAdmin)
+              const PopupMenuItem(value: '/admin', child: Text('Admin')),
+          ],
+        ),
+      ],
+    );
+  }
+}

flutter_client/test/shared/main_app_bar_actions_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/auth/auth_provider.dart';
+import 'package:minstrel/models/user.dart';
+import 'package:minstrel/shared/widgets/main_app_bar_actions.dart';
+import 'package:minstrel/theme/theme_data.dart';
+
+class _StubAuth extends AuthController {
+  _StubAuth(this._user);
+  final User? _user;
+  @override
+  Future<User?> build() async => _user;
+}
+
+Widget _harness({required User? user, required String currentRoute}) {
+  return ProviderScope(
+    overrides: [
+      authControllerProvider.overrideWith(() => _StubAuth(user)),
+    ],
+    child: MaterialApp(
+      theme: buildThemeData(),
+      home: Scaffold(
+        appBar: AppBar(
+          actions: [MainAppBarActions(currentRoute: currentRoute)],
+        ),
+      ),
+    ),
+  );
+}
+
+void main() {
+  const adminUser = User(id: 'u1', username: 'admin', isAdmin: true);
+  const regularUser = User(id: 'u2', username: 'alice', isAdmin: false);
+
+  testWidgets('renders Library + Search primary icons + kebab on /home',
+      (t) async {
+    await t.pumpWidget(_harness(user: regularUser, currentRoute: '/home'));
+    await t.pumpAndSettle();
+    expect(find.byKey(const Key('app_bar_library')), findsOneWidget);
+    expect(find.byKey(const Key('app_bar_search')), findsOneWidget);
+    expect(find.byKey(const Key('app_bar_home')), findsNothing);
+    expect(find.byKey(const Key('app_bar_overflow')), findsOneWidget);
+  });
+
+  testWidgets('suppresses Library icon when currentRoute is /library',
+      (t) async {
+    await t.pumpWidget(_harness(user: regularUser, currentRoute: '/library'));
+    await t.pumpAndSettle();
+    expect(find.byKey(const Key('app_bar_library')), findsNothing);
+    expect(find.byKey(const Key('app_bar_home')), findsOneWidget);
+  });
+
+  testWidgets('overflow includes Admin only for admin users', (t) async {
+    await t.pumpWidget(_harness(user: adminUser, currentRoute: '/home'));
+    await t.pumpAndSettle();
+    await t.tap(find.byKey(const Key('app_bar_overflow')));
+    await t.pumpAndSettle();
+    expect(find.text('Admin'), findsOneWidget);
+  });
+
+  testWidgets('overflow omits Admin for non-admin users', (t) async {
+    await t.pumpWidget(_harness(user: regularUser, currentRoute: '/home'));
+    await t.pumpAndSettle();
+    await t.tap(find.byKey(const Key('app_bar_overflow')));
+    await t.pumpAndSettle();
+    expect(find.text('Admin'), findsNothing);
+  });
+}