feat(02-02): create room providers, form screen, icon picker, and router routes

- Add Riverpod providers (roomWithStatsList, RoomActions) connecting to RoomsDao
- Create RoomFormScreen with name field, icon picker preview, create/edit modes
- Create IconPickerSheet bottom sheet with curated Material Icons grid
- Add nested GoRouter routes: /rooms/new, /rooms/:roomId, /rooms/:roomId/edit
- Add placeholder TaskListScreen and TaskFormScreen for Plan 03 routes
- Add 11 new German localization keys for room management UI
- Add flutter_reorderable_grid_view dependency

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

lib/features/rooms/presentation/icon_picker_sheet.dart

@@ -0,0 +1,94 @@
+import 'package:flutter/material.dart';
+
+import 'package:household_keeper/features/rooms/domain/room_icons.dart';
+
+/// Shows a modal bottom sheet with a grid of curated Material Icons.
+///
+/// Returns the selected icon name, or null if dismissed.
+Future<String?> showIconPickerSheet({
+  required BuildContext context,
+  String? selectedIconName,
+}) {
+  return showModalBottomSheet<String>(
+    context: context,
+    isScrollControlled: true,
+    builder: (context) => IconPickerSheet(
+      selectedIconName: selectedIconName,
+      onIconSelected: (name) => Navigator.of(context).pop(name),
+    ),
+  );
+}
+
+/// Grid of curated household Material Icons for room icon selection.
+class IconPickerSheet extends StatelessWidget {
+  const IconPickerSheet({
+    super.key,
+    this.selectedIconName,
+    required this.onIconSelected,
+  });
+
+  final String? selectedIconName;
+  final ValueChanged<String> onIconSelected;
+
+  @override
+  Widget build(BuildContext context) {
+    final theme = Theme.of(context);
+    final colorScheme = theme.colorScheme;
+
+    return SafeArea(
+      child: Padding(
+        padding: const EdgeInsets.all(16),
+        child: Column(
+          mainAxisSize: MainAxisSize.min,
+          children: [
+            // Drag handle
+            Container(
+              width: 32,
+              height: 4,
+              margin: const EdgeInsets.only(bottom: 16),
+              decoration: BoxDecoration(
+                color: colorScheme.onSurfaceVariant.withValues(alpha: 0.4),
+                borderRadius: BorderRadius.circular(2),
+              ),
+            ),
+            Text(
+              'Symbol w\u00e4hlen',
+              style: theme.textTheme.titleMedium,
+            ),
+            const SizedBox(height: 16),
+            GridView.count(
+              crossAxisCount: 5,
+              shrinkWrap: true,
+              physics: const NeverScrollableScrollPhysics(),
+              mainAxisSpacing: 8,
+              crossAxisSpacing: 8,
+              children: curatedRoomIcons.map((entry) {
+                final isSelected = entry.name == selectedIconName;
+                return InkWell(
+                  onTap: () => onIconSelected(entry.name),
+                  borderRadius: BorderRadius.circular(12),
+                  child: Container(
+                    decoration: BoxDecoration(
+                      color: isSelected
+                          ? colorScheme.primaryContainer
+                          : Colors.transparent,
+                      borderRadius: BorderRadius.circular(12),
+                    ),
+                    child: Icon(
+                      entry.icon,
+                      size: 28,
+                      color: isSelected
+                          ? colorScheme.onPrimaryContainer
+                          : colorScheme.onSurface,
+                    ),
+                  ),
+                );
+              }).toList(),
+            ),
+            const SizedBox(height: 8),
+          ],
+        ),
+      ),
+    );
+  }
+}