feat: Add Packet Log Screen for BLE packet logging and exporting

- Implemented PacketLogScreen to display and filter BLE packet logs.
- Added functionality to export logs as CSV and text files.
- Introduced clipboard copy feature for hex data.
- Implemented clear logs functionality with confirmation dialog.
- Enhanced MeshCoreBleService to log TX and RX packets with descriptions.
- Added BufferReader methods for reading unsigned and signed 16-bit integers (big-endian).
- Updated CayenneLppParser to read values as big-endian.
- Created MessageStorageService for persisting messages to local storage.
- Enhanced map markers to display telemetry data including voltage, humidity, and pressure.

lib/models/ble_packet_log.dart

@@ -0,0 +1,52 @@
+import 'dart:typed_data';
+
+/// Represents a logged BLE packet with timestamp and metadata
+class BlePacketLog {
+  final DateTime timestamp;
+  final Uint8List rawData;
+  final PacketDirection direction;
+  final int? responseCode;
+  final String? description;
+
+  BlePacketLog({
+    required this.timestamp,
+    required this.rawData,
+    required this.direction,
+    this.responseCode,
+    this.description,
+  });
+
+  /// Convert raw data to hex string for display
+  String get hexData {
+    return rawData.map((b) => b.toRadixString(16).padLeft(2, '0')).join(' ');
+  }
+
+  /// Get short summary of the packet
+  String get summary {
+    final dir = direction == PacketDirection.rx ? 'RX' : 'TX';
+    final code = responseCode != null ? '0x${responseCode!.toRadixString(16).padLeft(2, '0')}' : 'N/A';
+    return '[$dir] Code: $code, Size: ${rawData.length} bytes';
+  }
+
+  /// Convert to CSV format for export
+  String toCsvRow() {
+    final dir = direction == PacketDirection.rx ? 'RX' : 'TX';
+    final code = responseCode?.toString() ?? '';
+    final hex = hexData;
+    final desc = description ?? '';
+    return '${timestamp.toIso8601String()},$dir,${rawData.length},$code,"$hex","$desc"';
+  }
+
+  /// Convert to human-readable log format
+  String toLogString() {
+    final dir = direction == PacketDirection.rx ? 'RX' : 'TX';
+    final code = responseCode != null ? ' [0x${responseCode!.toRadixString(16).padLeft(2, '0')}]' : '';
+    final desc = description != null ? ' - $description' : '';
+    return '${timestamp.toIso8601String()} [$dir]$code ${rawData.length} bytes: $hexData$desc';
+  }
+}
+
+enum PacketDirection {
+  rx, // Received from device
+  tx, // Sent to device
+}