fix(flutter): clear analyze --fatal-infos errors from admin parity slice

CI caught six issues against the new admin slice:

- AsyncValue<T> in this Riverpod 3.3.1 codebase exposes `.value`
  (returns T?), not `.valueOrNull`. Switched the three admin readers
  to match the established convention (player_bar, queue_screen,
  now_playing_screen all use `.value`).
- home_screen.dart still has ctx.push calls in _albumsRow / _artistsRow
  (carousel tap handlers) — restored the go_router import that
  Task 2 over-eagerly removed.
- admin_user_edit_sheet.dart had a single-line `if (!await ...) return;`
  that violated curly_braces_in_flow_control_structures. Wrapped in
  braces.
- admin_quarantine_item.dart doc comment had `<top>` placeholders that
  the analyzer flagged as unintended HTML. Rephrased without angle
  brackets.

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

flutter_client/lib/admin/admin_requests_screen.dart

@@ -17,7 +17,7 @@ class AdminRequestsScreen extends ConsumerWidget {
     // Best-effort lookup for requester usernames. If the users provider
     // hasn't loaded yet, valueOrNull is null and rows fall back to the
     // UUID prefix; no blocking spinner.
-    final users = ref.watch(adminUsersProvider).valueOrNull ?? const <AdminUser>[];
+    final users = ref.watch(adminUsersProvider).value ?? const <AdminUser>[];
     final usersById = {for (final u in users) u.id: u};
 
     return Scaffold(

flutter_client/lib/admin/widgets/admin_user_edit_sheet.dart

@@ -151,7 +151,9 @@ class AdminUserEditSheet extends ConsumerWidget {
       message:
           'Permanently delete user "${user.username}" and all their data. '
           'Cannot be undone.',
-    )) return;
+    )) {
+      return;
+    }
     try {
       await users.delete(user.id);
       if (context.mounted) Navigator.pop(context);

flutter_client/lib/library/home_screen.dart

@@ -1,6 +1,7 @@
 import 'package:dio/dio.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:go_router/go_router.dart';
 
 import '../api/errors.dart';
 import '../models/album.dart';

flutter_client/lib/models/admin_quarantine_item.dart

@@ -55,9 +55,9 @@ class AdminQuarantineItem {
 
   final List<AdminQuarantineReport> reports;
 
-  /// One-line summary of the most-cited reason. Returns "<top>" when
-  /// only one reason exists or "<top> (+N more)" when there are
-  /// additional distinct reasons.
+  /// One-line summary of the most-cited reason. Returns just the top
+  /// reason when only one reason exists, or `top (+N more)` when there
+  /// are additional distinct reasons.
   String get topReasonSummary {
     if (reasonCounts.isEmpty) return '';
     final entries = reasonCounts.entries.toList()

flutter_client/lib/settings/settings_screen.dart

@@ -97,7 +97,7 @@ class _AdminSection extends ConsumerWidget {
   @override
   Widget build(BuildContext context, WidgetRef ref) {
     final fs = Theme.of(context).extension<FabledSwordTheme>()!;
-    final profile = ref.watch(_profileProvider).valueOrNull;
+    final profile = ref.watch(_profileProvider).value;
     if (profile == null || !profile.isAdmin) return const SizedBox.shrink();
     return Column(
       crossAxisAlignment: CrossAxisAlignment.stretch,

flutter_client/lib/shared/widgets/main_app_bar_actions.dart

@@ -17,7 +17,7 @@ class MainAppBarActions extends ConsumerWidget {
   @override
   Widget build(BuildContext context, WidgetRef ref) {
     final fs = Theme.of(context).extension<FabledSwordTheme>()!;
-    final user = ref.watch(authControllerProvider).valueOrNull;
+    final user = ref.watch(authControllerProvider).value;
     final isAdmin = user?.isAdmin ?? false;
 
     return Row(