feat: Add Mapy.cz Outdoor (OSM + LIDAR) base map layer

- New MapLayerType.mapyOutdoor with Referer header support
  (tile server rejects requests without mapy.com Referer)
- Headered layers get a dedicated NetworkTileProvider sharing
  the offline tile cache
- Offline region downloads pass layer headers through
  TileDownloadService

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

lib/providers/offline_tiles_provider.dart

@@ -266,6 +266,7 @@ class OfflineTilesProvider extends ChangeNotifier {
       maxZoom: _maxZoom,
       urlTemplate: _selectedLayer.urlTemplate,
       displayName: _selectedLayer.name,
+      headers: _selectedLayer.headers,
     );
 
     await for (final event in stream) {