feat(flutter/admin): landing screen with section cards + counts

ListView of three AdminSectionCard tiles (Requests / Quarantine /
Users) showing live counts from adminCountsProvider. Pull-to-refresh
re-fans-out to the three list endpoints. Admin/Quarantine/Users
sub-routes will land in subsequent commits.

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

flutter_client/lib/admin/admin_landing_screen.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 '../shared/widgets/main_app_bar_actions.dart';
+import '../theme/theme_extension.dart';
+import 'admin_providers.dart';
+import 'widgets/admin_section_card.dart';
+
+class AdminLandingScreen extends ConsumerWidget {
+  const AdminLandingScreen({super.key});
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final fs = Theme.of(context).extension<FabledSwordTheme>()!;
+    final counts = ref.watch(adminCountsProvider);
+    return Scaffold(
+      backgroundColor: fs.obsidian,
+      appBar: AppBar(
+        backgroundColor: fs.obsidian,
+        elevation: 0,
+        title: Text('Admin', style: TextStyle(color: fs.parchment)),
+        actions: const [MainAppBarActions(currentRoute: '/admin')],
+      ),
+      body: SafeArea(
+        child: counts.when(
+          loading: () => const Center(child: CircularProgressIndicator()),
+          error: (e, _) => Center(
+            child: Text('$e', style: TextStyle(color: fs.error)),
+          ),
+          data: (c) => RefreshIndicator(
+            onRefresh: () async => ref.refresh(adminCountsProvider.future),
+            child: ListView(
+              children: [
+                AdminSectionCard(
+                  key: const Key('admin_card_requests'),
+                  icon: Icons.inbox,
+                  title: 'Requests',
+                  subtitle: 'Approve or reject Lidarr requests',
+                  count: c.requests,
+                  onTap: () => context.push('/admin/requests'),
+                ),
+                AdminSectionCard(
+                  key: const Key('admin_card_quarantine'),
+                  icon: Icons.warning_amber,
+                  title: 'Quarantine',
+                  subtitle: 'Resolve scan failures',
+                  count: c.quarantine,
+                  onTap: () => context.push('/admin/quarantine'),
+                ),
+                AdminSectionCard(
+                  key: const Key('admin_card_users'),
+                  icon: Icons.people,
+                  title: 'Users',
+                  subtitle: 'Manage accounts and invites',
+                  count: c.users,
+                  onTap: () => context.push('/admin/users'),
+                ),
+              ],
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}

flutter_client/lib/admin/widgets/admin_section_card.dart

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+import 'package:flutter/material.dart';
+
+import '../../theme/theme_extension.dart';
+
+class AdminSectionCard extends StatelessWidget {
+  const AdminSectionCard({
+    super.key,
+    required this.icon,
+    required this.title,
+    required this.subtitle,
+    required this.count,
+    required this.onTap,
+  });
+
+  final IconData icon;
+  final String title;
+  final String subtitle;
+  final int count;
+  final VoidCallback onTap;
+
+  @override
+  Widget build(BuildContext context) {
+    final fs = Theme.of(context).extension<FabledSwordTheme>()!;
+    return Card(
+      color: fs.iron,
+      margin: const EdgeInsets.symmetric(horizontal: 12, vertical: 6),
+      child: ListTile(
+        leading: Icon(icon, color: fs.parchment),
+        title: Text(
+          title,
+          style: TextStyle(
+            color: fs.parchment,
+            fontFamily: 'Fraunces',
+            fontSize: 18,
+          ),
+        ),
+        subtitle: Text(subtitle, style: TextStyle(color: fs.ash)),
+        trailing: Container(
+          padding: const EdgeInsets.symmetric(horizontal: 10, vertical: 4),
+          decoration: BoxDecoration(
+            color: fs.bronze,
+            borderRadius: BorderRadius.circular(12),
+          ),
+          child: Text(
+            '$count',
+            style: TextStyle(color: fs.obsidian, fontWeight: FontWeight.w500),
+          ),
+        ),
+        onTap: onTap,
+      ),
+    );
+  }
+}

flutter_client/test/admin/admin_landing_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/admin/admin_landing_screen.dart';
+import 'package:minstrel/admin/admin_providers.dart';
+import 'package:minstrel/auth/auth_provider.dart';
+import 'package:minstrel/models/user.dart';
+import 'package:minstrel/theme/theme_data.dart';
+
+class _StubAuth extends AuthController {
+  @override
+  Future<User?> build() async =>
+      const User(id: 'u1', username: 'admin', isAdmin: true);
+}
+
+void main() {
+  testWidgets('renders three section cards with counts from provider',
+      (t) async {
+    await t.pumpWidget(
+      ProviderScope(
+        overrides: [
+          authControllerProvider.overrideWith(() => _StubAuth()),
+          adminCountsProvider.overrideWith(
+            (_) async => const AdminCounts(
+              requests: 3,
+              quarantine: 1,
+              users: 5,
+            ),
+          ),
+        ],
+        child: MaterialApp(
+          theme: buildThemeData(),
+          home: const AdminLandingScreen(),
+        ),
+      ),
+    );
+    await t.pumpAndSettle();
+    expect(find.byKey(const Key('admin_card_requests')), findsOneWidget);
+    expect(find.byKey(const Key('admin_card_quarantine')), findsOneWidget);
+    expect(find.byKey(const Key('admin_card_users')), findsOneWidget);
+    expect(find.text('3'), findsOneWidget);
+    expect(find.text('1'), findsOneWidget);
+    expect(find.text('5'), findsOneWidget);
+  });
+}