feat: Add Sensor telemetry alerts

ref:

test/services/notification_service_test.dart

@@ -0,0 +1,25 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:meshcore_sar_app/services/notification_service.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+
+  setUp(() {
+    SharedPreferences.setMockInitialValues({});
+  });
+
+  test('discovery notification preference persists independently', () async {
+    final service = NotificationService();
+
+    await service.setMessageNotificationsEnabled(true);
+    await service.setDiscoveryNotificationsEnabled(false);
+
+    final prefs = await SharedPreferences.getInstance();
+
+    expect(service.messageNotificationsEnabled, isTrue);
+    expect(service.discoveryNotificationsEnabled, isFalse);
+    expect(prefs.getBool('notifications_messages_enabled'), isTrue);
+    expect(prefs.getBool('notifications_discovery_enabled'), isFalse);
+  });
+}