Add shared UI components for mesh application

- Introduced `mesh_ui.dart` with reusable widgets including SectionHeader, MeshCard, StatusChip, StatTile, AvatarCircle, SignalBars, RouteChip, PulseDot, BottomSheetHeader, ErrorRetryCard, and ListEntrance.
- Implemented `path_map_ui.dart` for path map screens, featuring path distance calculations, playback controls, and a summary list of observed paths.
- Created `themed_map_tile_layer.dart` for shared cached map tiles with automatic dark-mode treatment.

lib/widgets/themed_map_tile_layer.dart

@@ -0,0 +1,60 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_map/flutter_map.dart';
+
+import '../services/map_tile_cache_service.dart';
+
+/// Shared cached map tiles with an automatic dark-mode treatment.
+///
+/// The dark style transforms the existing OpenStreetMap raster tiles, so light
+/// and dark maps share the same offline cache and network requests.
+class ThemedMapTileLayer extends StatelessWidget {
+  final MapTileCacheService tileCache;
+  final double opacity;
+
+  const ThemedMapTileLayer({
+    super.key,
+    required this.tileCache,
+    this.opacity = 1,
+  });
+
+  static const ColorFilter _darkMapFilter = ColorFilter.matrix([
+    -0.0850,
+    -0.2861,
+    -0.0289,
+    0,
+    120,
+    -0.0957,
+    -0.3218,
+    -0.0325,
+    0,
+    140,
+    -0.1169,
+    -0.3934,
+    -0.0397,
+    0,
+    170,
+    0,
+    0,
+    0,
+    1,
+    0,
+  ]);
+
+  @override
+  Widget build(BuildContext context) {
+    Widget layer = TileLayer(
+      urlTemplate: kMapTileUrlTemplate,
+      tileProvider: tileCache.tileProvider,
+      userAgentPackageName: MapTileCacheService.userAgentPackageName,
+      maxZoom: 19,
+    );
+
+    if (Theme.of(context).brightness == Brightness.dark) {
+      layer = ColorFiltered(colorFilter: _darkMapFilter, child: layer);
+    }
+    if (opacity < 1) {
+      layer = Opacity(opacity: opacity, child: layer);
+    }
+    return layer;
+  }
+}