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>
Jean-Luc Makiola
32e61e4bec