feat: Implement command queue for BLE command handling

- Added BleCommandQueue to manage command serialization and responses in BleCommandSender.
- Updated writeData, writeDataAndWaitForAck, and writeDataAndWaitForResponse methods to utilize the command queue.
- Enhanced BleResponseHandler to complete commands based on responses received from the BLE device.
- Introduced new commands for channel management, including getChannel and setChannel.
- Created LocationTrailLayer and TrailControls widgets for displaying and managing location trails on the map.
- Added PermissionRequestDialog to handle location permission requests on app startup.
- Updated LocationTrackingService to allow GPS tracking without a BLE connection.

lib/models/channel.dart

@@ -0,0 +1,75 @@
+/// Channel model - represents a communication channel
+class Channel {
+  final int index;
+  final String name;
+  final int? flags;
+
+  Channel({
+    required this.index,
+    required this.name,
+    this.flags,
+  });
+
+  /// Display name for the channel
+  /// Returns "Public" for channel 0, otherwise returns the custom name or "Channel N"
+  String get displayName {
+    if (index == 0) {
+      return name.isEmpty ? 'Public' : name;
+    }
+    return name.isEmpty ? 'Channel $index' : name;
+  }
+
+  /// Check if channel is the public channel (index 0)
+  bool get isPublicChannel => index == 0;
+
+  /// Check if channel has a custom name
+  bool get hasCustomName => name.isNotEmpty;
+
+  /// Create from JSON
+  factory Channel.fromJson(Map<String, dynamic> json) {
+    return Channel(
+      index: json['index'] as int,
+      name: json['name'] as String? ?? '',
+      flags: json['flags'] as int?,
+    );
+  }
+
+  /// Convert to JSON
+  Map<String, dynamic> toJson() {
+    return {
+      'index': index,
+      'name': name,
+      'flags': flags,
+    };
+  }
+
+  /// Create a copy with modified fields
+  Channel copyWith({
+    int? index,
+    String? name,
+    int? flags,
+  }) {
+    return Channel(
+      index: index ?? this.index,
+      name: name ?? this.name,
+      flags: flags ?? this.flags,
+    );
+  }
+
+  @override
+  String toString() {
+    return 'Channel(index: $index, name: $name, flags: $flags)';
+  }
+
+  @override
+  bool operator ==(Object other) {
+    if (identical(this, other)) return true;
+    return other is Channel &&
+        other.index == index &&
+        other.name == name &&
+        other.flags == flags;
+  }
+
+  @override
+  int get hashCode => Object.hash(index, name, flags);
+}

lib/models/location_trail.dart

@@ -0,0 +1,106 @@
+import 'package:latlong2/latlong.dart';
+
+/// Represents a single point in a location trail
+class TrailPoint {
+  final LatLng position;
+  final DateTime timestamp;
+  final double? accuracy;
+  final double? speed;
+
+  TrailPoint({
+    required this.position,
+    required this.timestamp,
+    this.accuracy,
+    this.speed,
+  });
+
+  Map<String, dynamic> toJson() => {
+        'lat': position.latitude,
+        'lon': position.longitude,
+        'timestamp': timestamp.toIso8601String(),
+        'accuracy': accuracy,
+        'speed': speed,
+      };
+
+  factory TrailPoint.fromJson(Map<String, dynamic> json) {
+    return TrailPoint(
+      position: LatLng(json['lat'] as double, json['lon'] as double),
+      timestamp: DateTime.parse(json['timestamp'] as String),
+      accuracy: json['accuracy'] as double?,
+      speed: json['speed'] as double?,
+    );
+  }
+}
+
+/// Represents a location trail (breadcrumb trail) on the map
+class LocationTrail {
+  final String id;
+  final List<TrailPoint> points;
+  final DateTime startTime;
+  DateTime? endTime;
+  bool isActive;
+
+  LocationTrail({
+    required this.id,
+    List<TrailPoint>? points,
+    DateTime? startTime,
+    this.endTime,
+    this.isActive = true,
+  })  : points = points ?? [],
+        startTime = startTime ?? DateTime.now();
+
+  /// Add a new point to the trail
+  void addPoint(TrailPoint point) {
+    points.add(point);
+  }
+
+  /// Get total distance traveled in meters
+  double get totalDistance {
+    if (points.length < 2) return 0;
+
+    final distance = Distance();
+    double total = 0;
+
+    for (int i = 0; i < points.length - 1; i++) {
+      total += distance.as(
+        LengthUnit.Meter,
+        points[i].position,
+        points[i + 1].position,
+      );
+    }
+
+    return total;
+  }
+
+  /// Get duration of the trail
+  Duration get duration {
+    if (points.isEmpty) return Duration.zero;
+    final end = endTime ?? DateTime.now();
+    return end.difference(startTime);
+  }
+
+  /// Get list of LatLng points for rendering
+  List<LatLng> get latLngPoints => points.map((p) => p.position).toList();
+
+  Map<String, dynamic> toJson() => {
+        'id': id,
+        'points': points.map((p) => p.toJson()).toList(),
+        'startTime': startTime.toIso8601String(),
+        'endTime': endTime?.toIso8601String(),
+        'isActive': isActive,
+      };
+
+  factory LocationTrail.fromJson(Map<String, dynamic> json) {
+    return LocationTrail(
+      id: json['id'] as String,
+      points: (json['points'] as List)
+          .map((p) => TrailPoint.fromJson(p as Map<String, dynamic>))
+          .toList(),
+      startTime: DateTime.parse(json['startTime'] as String),
+      endTime: json['endTime'] != null
+          ? DateTime.parse(json['endTime'] as String)
+          : null,
+      isActive: json['isActive'] as bool? ?? true,
+    );
+  }
+}