Add transmission timing details

lib/models/message_reception_details.dart

@@ -0,0 +1,63 @@
+class MessageReceptionDetails {
+  final DateTime capturedAt;
+  final DateTime? packetLoggedAt;
+  final int? rssiDbm;
+  final double? snrDb;
+  final List<int>? pathBytes;
+  final int? senderToReceiptMs;
+  final int? estimatedTransmitMs;
+  final int? postTransmitDelayMs;
+
+  const MessageReceptionDetails({
+    required this.capturedAt,
+    this.packetLoggedAt,
+    this.rssiDbm,
+    this.snrDb,
+    this.pathBytes,
+    this.senderToReceiptMs,
+    this.estimatedTransmitMs,
+    this.postTransmitDelayMs,
+  });
+
+  String? get pathBytesHex => pathBytes == null || pathBytes!.isEmpty
+      ? null
+      : pathBytes!.map((b) => b.toRadixString(16).padLeft(2, '0')).join(':');
+
+  Map<String, dynamic> toJson() {
+    return {
+      'capturedAtMillis': capturedAt.millisecondsSinceEpoch,
+      'packetLoggedAtMillis': packetLoggedAt?.millisecondsSinceEpoch,
+      'rssiDbm': rssiDbm,
+      'snrDb': snrDb,
+      'pathBytes': pathBytes,
+      'senderToReceiptMs': senderToReceiptMs,
+      'estimatedTransmitMs': estimatedTransmitMs,
+      'postTransmitDelayMs': postTransmitDelayMs,
+    };
+  }
+
+  static MessageReceptionDetails? fromJson(Map<String, dynamic> json) {
+    final capturedAtMillis = json['capturedAtMillis'];
+    if (capturedAtMillis is! int) {
+      return null;
+    }
+
+    final pathBytes = json['pathBytes'];
+    return MessageReceptionDetails(
+      capturedAt: DateTime.fromMillisecondsSinceEpoch(capturedAtMillis),
+      packetLoggedAt: json['packetLoggedAtMillis'] is int
+          ? DateTime.fromMillisecondsSinceEpoch(
+              json['packetLoggedAtMillis'] as int,
+            )
+          : null,
+      rssiDbm: json['rssiDbm'] as int?,
+      snrDb: (json['snrDb'] as num?)?.toDouble(),
+      pathBytes: pathBytes is List
+          ? pathBytes.whereType<num>().map((b) => b.toInt()).toList()
+          : null,
+      senderToReceiptMs: json['senderToReceiptMs'] as int?,
+      estimatedTransmitMs: json['estimatedTransmitMs'] as int?,
+      postTransmitDelayMs: json['postTransmitDelayMs'] as int?,
+    );
+  }
+}