Add trace button to message bubble

lib/services/mesh_map_nodes_service.dart

@@ -0,0 +1,68 @@
+import 'dart:convert';
+import 'package:http/http.dart' as http;
+
+class MeshMapNode {
+  final int type;
+  final String name;
+  final String publicKey;
+  final double latitude;
+  final double longitude;
+  final int updatedAtMs;
+
+  const MeshMapNode({
+    required this.type,
+    required this.name,
+    required this.publicKey,
+    required this.latitude,
+    required this.longitude,
+    required this.updatedAtMs,
+  });
+
+  factory MeshMapNode.fromJson(Map<String, dynamic> json) {
+    return MeshMapNode(
+      type: (json['type'] as num?)?.toInt() ?? 0,
+      name: (json['name'] as String?)?.trim() ?? 'Unknown',
+      publicKey: ((json['public_key'] as String?) ?? '').toLowerCase(),
+      latitude: (json['latitude'] as num?)?.toDouble() ?? 0.0,
+      longitude: (json['longitude'] as num?)?.toDouble() ?? 0.0,
+      updatedAtMs: (json['updated_at'] as num?)?.toInt() ?? 0,
+    );
+  }
+}
+
+class MeshMapNodesService {
+  static const String _nodesEndpoint = 'https://api.meshcore.nz/api/v1/map/nodes';
+  static const Duration _cacheTtl = Duration(minutes: 2);
+  static List<MeshMapNode>? _cachedNodes;
+  static DateTime? _cachedAt;
+
+  static Future<List<MeshMapNode>> fetchNodes({bool forceRefresh = false}) async {
+    final now = DateTime.now();
+    if (!forceRefresh &&
+        _cachedNodes != null &&
+        _cachedAt != null &&
+        now.difference(_cachedAt!) < _cacheTtl) {
+      return _cachedNodes!;
+    }
+
+    final response = await http
+        .get(Uri.parse(_nodesEndpoint))
+        .timeout(const Duration(seconds: 12));
+    if (response.statusCode < 200 || response.statusCode >= 300) {
+      throw Exception('Map nodes API returned ${response.statusCode}');
+    }
+
+    final decoded = jsonDecode(response.body) as Map<String, dynamic>;
+    final nodesRaw = decoded['nodes'] as List<dynamic>? ?? const [];
+
+    final nodes = nodesRaw
+        .whereType<Map<String, dynamic>>()
+        .map(MeshMapNode.fromJson)
+        .where((n) => n.publicKey.isNotEmpty && n.latitude != 0 && n.longitude != 0)
+        .toList();
+
+    _cachedNodes = nodes;
+    _cachedAt = now;
+    return nodes;
+  }
+}