fix: use ValueKey<String> for reorderable grid and add status bar padding

flutter_reorderable_grid_view requires String keys, not int. Also
adds safe area top padding so the room grid doesn't overlap the
system status bar.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

test/shell/app_shell_test.dart

@@ -1,4 +1,3 @@
-// ignore_for_file: scoped_providers_should_specify_dependencies
 import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:flutter_test/flutter_test.dart';