refactor: extract BLE protocol stack into meshcore_client package

Move BLE communication layer (command queue, frame parser/builder,
protocol constants, data models) into a standalone reusable Dart package
at ../meshcore_client. App model files become thin re-export wrappers,
keeping all existing consumers working without import changes.

lib/models/contact_telemetry.dart

@@ -1,76 +1 @@
-import 'package:latlong2/latlong.dart';
-
-/// Contact telemetry data from MeshCore device
-class ContactTelemetry {
-  final LatLng? gpsLocation;
-  final double? batteryPercentage;
-  final double? batteryMilliVolts;
-  final double? temperature;
-  final DateTime timestamp;
-
-  // Additional sensor data
-  final double? humidity;
-  final double? pressure;
-  final Map<String, dynamic>? extraSensorData;
-
-  ContactTelemetry({
-    this.gpsLocation,
-    this.batteryPercentage,
-    this.batteryMilliVolts,
-    this.temperature,
-    required this.timestamp,
-    this.humidity,
-    this.pressure,
-    this.extraSensorData,
-  });
-
-  /// Check if telemetry data is recent (within last 5 minutes)
-  bool get isRecent {
-    return DateTime.now().difference(timestamp).inMinutes < 5;
-  }
-
-  /// Check if battery level is low (< 20%)
-  bool get isLowBattery {
-    return batteryPercentage != null && batteryPercentage! < 20.0;
-  }
-
-  /// Check if battery level is critical (< 10%)
-  bool get isCriticalBattery {
-    return batteryPercentage != null && batteryPercentage! < 10.0;
-  }
-
-  /// Get battery status color indicator
-  String get batteryStatus {
-    if (batteryPercentage == null) return 'unknown';
-    if (batteryPercentage! > 50) return 'good';
-    if (batteryPercentage! > 20) return 'medium';
-    return 'low';
-  }
-
-  ContactTelemetry copyWith({
-    LatLng? gpsLocation,
-    double? batteryPercentage,
-    double? batteryMilliVolts,
-    double? temperature,
-    DateTime? timestamp,
-    double? humidity,
-    double? pressure,
-    Map<String, dynamic>? extraSensorData,
-  }) {
-    return ContactTelemetry(
-      gpsLocation: gpsLocation ?? this.gpsLocation,
-      batteryPercentage: batteryPercentage ?? this.batteryPercentage,
-      batteryMilliVolts: batteryMilliVolts ?? this.batteryMilliVolts,
-      temperature: temperature ?? this.temperature,
-      timestamp: timestamp ?? this.timestamp,
-      humidity: humidity ?? this.humidity,
-      pressure: pressure ?? this.pressure,
-      extraSensorData: extraSensorData ?? this.extraSensorData,
-    );
-  }
-
-  @override
-  String toString() {
-    return 'ContactTelemetry(gps: $gpsLocation, battery: $batteryPercentage%, temp: $temperature°C, time: $timestamp)';
-  }
-}
+export 'package:meshcore_client/meshcore_client.dart' show ContactTelemetry;