feat(02-02): build rooms screen with reorderable card grid and room card

- Replace placeholder RoomsScreen with ConsumerWidget watching roomWithStatsProvider
- Create RoomCard with icon, name, due count badge, cleanliness progress bar
- 2-column ReorderableBuilder grid with drag-and-drop reorder
- Empty state, loading, error states with retry
- Long-press menu for edit/delete with confirmation dialog
- FAB for room creation navigation
- Update app_shell_test with provider override for rooms stream

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

lib/features/rooms/presentation/rooms_screen.dart

@@ -1,13 +1,64 @@
 import 'package:flutter/material.dart';
+import 'package:flutter_reorderable_grid_view/widgets/widgets.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:go_router/go_router.dart';
 
+import 'package:household_keeper/features/rooms/data/rooms_dao.dart';
+import 'package:household_keeper/features/rooms/presentation/room_card.dart';
+import 'package:household_keeper/features/rooms/presentation/room_providers.dart';
 import 'package:household_keeper/l10n/app_localizations.dart';
 
-class RoomsScreen extends StatelessWidget {
+/// Rooms screen showing a 2-column reorderable card grid of rooms.
+///
+/// Displays an empty state when no rooms exist, with a button to create one.
+/// FAB always visible for quick room creation.
+class RoomsScreen extends ConsumerWidget {
   const RoomsScreen({super.key});
 
   @override
-  Widget build(BuildContext context) {
+  Widget build(BuildContext context, WidgetRef ref) {
     final l10n = AppLocalizations.of(context);
+    final asyncRooms = ref.watch(roomWithStatsListProvider);
+
+    return Scaffold(
+      body: asyncRooms.when(
+        data: (rooms) {
+          if (rooms.isEmpty) {
+            return _EmptyState(l10n: l10n);
+          }
+          return _RoomGrid(rooms: rooms);
+        },
+        loading: () => const Center(child: CircularProgressIndicator()),
+        error: (error, stack) => Center(
+          child: Column(
+            mainAxisSize: MainAxisSize.min,
+            children: [
+              Text('Fehler: $error'),
+              const SizedBox(height: 16),
+              FilledButton.tonal(
+                onPressed: () => ref.invalidate(roomWithStatsListProvider),
+                child: const Text('Erneut versuchen'),
+              ),
+            ],
+          ),
+        ),
+      ),
+      floatingActionButton: FloatingActionButton(
+        onPressed: () => context.go('/rooms/new'),
+        child: const Icon(Icons.add),
+      ),
+    );
+  }
+}
+
+/// Empty state shown when no rooms have been created yet.
+class _EmptyState extends StatelessWidget {
+  const _EmptyState({required this.l10n});
+
+  final AppLocalizations l10n;
+
+  @override
+  Widget build(BuildContext context) {
     final theme = Theme.of(context);
 
     return Center(
@@ -37,9 +88,7 @@ class RoomsScreen extends StatelessWidget {
             ),
             const SizedBox(height: 24),
             FilledButton.tonal(
-              onPressed: () {
-                // Room creation will be implemented in Phase 2
-              },
+              onPressed: () => context.go('/rooms/new'),
               child: Text(l10n.roomsEmptyAction),
             ),
           ],
@@ -48,3 +97,92 @@ class RoomsScreen extends StatelessWidget {
     );
   }
 }
+
+/// 2-column reorderable grid of room cards.
+class _RoomGrid extends ConsumerStatefulWidget {
+  const _RoomGrid({required this.rooms});
+
+  final List<RoomWithStats> rooms;
+
+  @override
+  ConsumerState<_RoomGrid> createState() => _RoomGridState();
+}
+
+class _RoomGridState extends ConsumerState<_RoomGrid> {
+  final _scrollController = ScrollController();
+  final _gridViewKey = GlobalKey();
+
+  @override
+  void dispose() {
+    _scrollController.dispose();
+    super.dispose();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final l10n = AppLocalizations.of(context);
+    final children = widget.rooms.map((rws) {
+      return RoomCard(
+        key: ValueKey(rws.room.id),
+        roomWithStats: rws,
+        onEdit: () => context.go('/rooms/${rws.room.id}/edit'),
+        onDelete: () => _showDeleteConfirmation(context, rws, l10n),
+      );
+    }).toList();
+
+    return ReorderableBuilder<Widget>(
+      scrollController: _scrollController,
+      onReorder: (ReorderedListFunction<Widget> reorderFunc) {
+        final reordered = reorderFunc(children);
+        final newOrder = reordered
+            .map((w) => (w.key! as ValueKey<int>).value)
+            .toList();
+        ref.read(roomActionsProvider.notifier).reorderRooms(newOrder);
+      },
+      builder: (reorderableChildren) {
+        return GridView.count(
+          key: _gridViewKey,
+          controller: _scrollController,
+          crossAxisCount: 2,
+          padding: const EdgeInsets.all(12),
+          mainAxisSpacing: 8,
+          crossAxisSpacing: 8,
+          childAspectRatio: 1.0,
+          children: reorderableChildren,
+        );
+      },
+      children: children,
+    );
+  }
+
+  void _showDeleteConfirmation(
+    BuildContext context,
+    RoomWithStats rws,
+    AppLocalizations l10n,
+  ) {
+    showDialog(
+      context: context,
+      builder: (ctx) => AlertDialog(
+        title: Text(l10n.roomDeleteConfirmTitle),
+        content: Text(l10n.roomDeleteConfirmMessage),
+        actions: [
+          TextButton(
+            onPressed: () => Navigator.pop(ctx),
+            child: Text(l10n.cancel),
+          ),
+          FilledButton(
+            onPressed: () {
+              Navigator.pop(ctx);
+              ref.read(roomActionsProvider.notifier).deleteRoom(rws.room.id);
+            },
+            style: FilledButton.styleFrom(
+              backgroundColor: Theme.of(context).colorScheme.error,
+              foregroundColor: Theme.of(context).colorScheme.onError,
+            ),
+            child: Text(l10n.roomDeleteConfirmAction),
+          ),
+        ],
+      ),
+    );
+  }
+}