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/screens/offline_map_screen.dart

@@ -114,6 +114,9 @@ class _OfflineMapScreenState extends State<OfflineMapScreen> {
                 children: [
                   TileLayer(
                     urlTemplate: provider.selectedLayer.urlTemplate,
+                    tileProvider: NetworkTileProvider(
+                      headers: provider.selectedLayer.headers ?? const {},
+                    ),
                     userAgentPackageName: 'com.meshcore.sar',
                     maxZoom: provider.selectedLayer.maxZoom,
                   ),