feat: Share contact as meshcore:// URL via clipboard

lib/providers/connection_provider.dart

@@ -2201,7 +2201,24 @@ class ConnectionProvider with ChangeNotifier {
     }
   }
 
-  /// Request fresh device info (triggers SelfInfo response)
+  /// Export a contact as a meshcore:// share URL.
+  /// Pass null to export self.
+  Future<String?> exportContactUrl(Uint8List? publicKey) async {
+    if (!_activeService.isConnected) return null;
+    try {
+      final frame = await _activeService.exportContact(publicKey);
+      final hex = frame
+          .map((b) => b.toRadixString(16).padLeft(2, '0'))
+          .join();
+      return 'meshcore://$hex';
+    } catch (e) {
+      debugPrint('⚠️ [Provider] exportContact failed: $e');
+      _error = 'Failed to export contact: $e';
+      notifyListeners();
+      return null;
+    }
+  }
+
   /// Read custom variables from device (GPS mode, sensor settings, etc.)
   Future<Map<String, String>> getCustomVars() async {
     if (!_activeService.isConnected) {

lib/widgets/contacts/contact_tile.dart

@@ -1,6 +1,5 @@
-import 'dart:typed_data';
-
 import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
 import 'package:provider/provider.dart';
 import 'package:geolocator/geolocator.dart';
 import 'package:latlong2/latlong.dart';
@@ -371,6 +370,35 @@ class ContactTile extends StatelessWidget {
                     }
                   },
                 ),
+              if (!contact.isChannel)
+                ListTile(
+                  leading: const Icon(Icons.share_outlined),
+                  title: const Text('Share Contact'),
+                  onTap: () async {
+                    Navigator.pop(sheetContext);
+                    final connectionProvider =
+                        context.read<ConnectionProvider>();
+                    final url = await connectionProvider.exportContactUrl(
+                      contact.publicKey,
+                    );
+                    if (url != null && context.mounted) {
+                      await Clipboard.setData(ClipboardData(text: url));
+                      if (context.mounted) {
+                        ScaffoldMessenger.of(context).showSnackBar(
+                          const SnackBar(
+                            content: Text('Contact link copied to clipboard'),
+                          ),
+                        );
+                      }
+                    } else if (context.mounted) {
+                      ScaffoldMessenger.of(context).showSnackBar(
+                        const SnackBar(
+                          content: Text('Failed to export contact'),
+                        ),
+                      );
+                    }
+                  },
+                ),
               ListTile(
                 leading: const Icon(Icons.message_outlined),
                 title: Text(l10n.messages),