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/l10n/app_localizations_de.dart

@@ -67,4 +67,40 @@ class AppLocalizationsDe extends AppLocalizations {
   String aboutVersion(String version) {
     return 'Version $version';
   }
+
+  @override
+  String get roomFormCreateTitle => 'Raum erstellen';
+
+  @override
+  String get roomFormEditTitle => 'Raum bearbeiten';
+
+  @override
+  String get roomFormNameLabel => 'Raumname';
+
+  @override
+  String get roomFormNameHint => 'z.B. Küche, Badezimmer...';
+
+  @override
+  String get roomFormNameRequired => 'Bitte einen Namen eingeben';
+
+  @override
+  String get roomFormIconLabel => 'Symbol wählen';
+
+  @override
+  String get roomDeleteConfirmTitle => 'Raum löschen?';
+
+  @override
+  String get roomDeleteConfirmMessage =>
+      'Der Raum und alle zugehörigen Aufgaben werden unwiderruflich gelöscht.';
+
+  @override
+  String get roomDeleteConfirmAction => 'Löschen';
+
+  @override
+  String roomCardDueCount(int count) {
+    return '$count fällig';
+  }
+
+  @override
+  String get cancel => 'Abbrechen';
 }