Add contact settings and discovery features

- Implemented contact settings in localization files for Swedish, Ukrainian, and Chinese.
- Added new DiscoveryContact model to handle discovered contacts.
- Created DiscoveryScreen to display discovered contacts with filtering and sorting options.
- Integrated contact discovery storage to persist discovered contacts.
- Updated settings screen to include options for automatic contact addition.
- Enhanced app bar and list filter widgets for better user experience.
- Fixed variable naming inconsistencies in contact model.

lib/models/contact.dart

@@ -183,7 +183,7 @@ class Contact {
             )
           : Uint8List(0);
       final name = readCString(data, contactNameOffset, maxNameSize);
-      final lastmod = readUint32LE(data, contactLastmodOffset);
+      final lastmod = readUint32LE(data, contactLastModOffset);
 
       double? lat, lon;
       final latRaw = readInt32LE(data, contactLatOffset);

lib/models/discovery_contact.dart

@@ -0,0 +1,137 @@
+import 'dart:typed_data';
+import '../connector/meshcore_protocol.dart';
+
+class DiscoveryContact {
+  final Uint8List publicKey;
+  final String name;
+  final int type;
+  final int pathLength; // -1 = flood, 0+ = direct hops (from device)
+  final Uint8List path; // Path bytes from device
+  final double? latitude;
+  final double? longitude;
+  final DateTime lastSeen;
+
+  DiscoveryContact({
+    required this.publicKey,
+    required this.name,
+    required this.type,
+    required this.pathLength,
+    required this.path,
+    this.latitude,
+    this.longitude,
+    required this.lastSeen,
+  });
+
+  String get publicKeyHex => pubKeyToHex(publicKey);
+
+  String get typeLabel {
+    switch (type) {
+      case advTypeChat:
+        return 'Chat';
+      case advTypeRepeater:
+        return 'Repeater';
+      case advTypeRoom:
+        return 'Room';
+      case advTypeSensor:
+        return 'Sensor';
+      default:
+        return 'Unknown';
+    }
+  }
+
+  String get pathLabel {
+    if (pathLength < 0) return 'Flood';
+    if (pathLength == 0) return 'Direct';
+    return '$pathLength hops';
+  }
+
+  bool get hasLocation => latitude != null && longitude != null;
+
+  DiscoveryContact copyWith({
+    Uint8List? publicKey,
+    String? name,
+    int? type,
+    int? pathLength,
+    Uint8List? path,
+    double? latitude,
+    double? longitude,
+    DateTime? lastSeen,
+  }) {
+    return DiscoveryContact(
+      publicKey: publicKey ?? this.publicKey,
+      name: name ?? this.name,
+      type: type ?? this.type,
+      pathLength: pathLength ?? this.pathLength,
+      path: path ?? this.path,
+      latitude: latitude ?? this.latitude,
+      longitude: longitude ?? this.longitude,
+      lastSeen: lastSeen ?? this.lastSeen,
+    );
+  }
+
+  String get pathIdList {
+    final pathBytes = path;
+    if (pathBytes.isEmpty) return '';
+    final parts = <String>[];
+    final groupSize = pathHashSize;
+    for (int i = 0; i < pathBytes.length; i += groupSize) {
+      final end = (i + groupSize) <= pathBytes.length
+          ? (i + groupSize)
+          : pathBytes.length;
+      final chunk = pathBytes.sublist(i, end);
+      parts.add(
+        chunk
+            .map((b) => b.toRadixString(16).padLeft(2, '0').toUpperCase())
+            .join(),
+      );
+    }
+    return parts.join(',');
+  }
+
+  String get shortPubKeyHex {
+    return "<${publicKeyHex.substring(0, 8)}...${publicKeyHex.substring(publicKeyHex.length - 8)}>";
+  }
+
+  Uint8List? get traceRouteBytes {
+    final pathBytes = path;
+    Uint8List? traceBytes;
+
+    if (pathBytes.isEmpty) {
+      traceBytes = Uint8List(1);
+      traceBytes[0] = publicKey[0];
+      return traceBytes;
+    }
+
+    if (type == advTypeRepeater || type == advTypeRoom) {
+      final len = (pathBytes.length + pathBytes.length + 1);
+      traceBytes = Uint8List(len);
+      traceBytes[pathBytes.length] = publicKey[0];
+      for (int i = 0; i < pathBytes.length; i++) {
+        traceBytes[i] = pathBytes[i];
+        if (i < pathBytes.length) {
+          traceBytes[len - 1 - i] = pathBytes[i];
+        }
+      }
+    } else {
+      if (pathBytes.length < 2) {
+        return pathBytes[0] == 0 ? null : pathBytes;
+      }
+      final len = (pathBytes.length + pathBytes.length - 1);
+      traceBytes = Uint8List(len);
+      for (int i = 0; i < pathBytes.length; i++) {
+        traceBytes[i] = pathBytes[i];
+        if (i < pathBytes.length - 1) {
+          traceBytes[len - 1 - i] = pathBytes[i];
+        }
+      }
+    }
+    return traceBytes;
+  }
+
+  @override
+  bool operator ==(Object other) =>
+      other is DiscoveryContact && publicKeyHex == other.publicKeyHex;
+
+  @override
+  int get hashCode => publicKeyHex.hashCode;
+}