feat: implement ble tag scanning

lib/domain/models/tag.dart

@@ -3,13 +3,15 @@ import 'position.dart';
 class Tag {
   const Tag({
     required this.id,
+    required this.tagId,
     required this.name,
     this.currentRoomId,
     this.lastPosition,
     this.lastSeen,
   });
 
-  final String id;
+  final int id;
+  final String tagId; // BLE beacon advertised identifier
   final String name;
   final String? currentRoomId;
   final Position? lastPosition;
@@ -18,6 +20,7 @@ class Tag {
   Tag copyWith({String? name, String? currentRoomId, Position? lastPosition, DateTime? lastSeen}) =>
       Tag(
         id: id,
+        tagId: tagId,
         name: name ?? this.name,
         currentRoomId: currentRoomId ?? this.currentRoomId,
         lastPosition: lastPosition ?? this.lastPosition,
@@ -26,6 +29,7 @@ class Tag {
 
   Map<String, dynamic> toJson() => {
         'id': id,
+        'tag_id': tagId,
         'name': name,
         'current_room_id': currentRoomId,
         'last_position': lastPosition?.toJson(),
@@ -33,7 +37,8 @@ class Tag {
       };
 
   factory Tag.fromJson(Map<String, dynamic> json) => Tag(
-        id: json['id'] as String,
+        id: json['id'] as int,
+        tagId: json['tag_id'] as String,
         name: json['name'] as String,
         currentRoomId: json['current_room_id'] as String?,
         lastPosition: json['last_position'] == null