replaced account data singleton with a session model

lib/api/marianumconnect/queries/telemetry_heartbeat/telemetry_device_id.dart

@@ -1,7 +1,7 @@
-import 'dart:math';
-
 import 'package:flutter_secure_storage/flutter_secure_storage.dart';
 
+import '../../../../utils/random_id.dart';
+
 /// A stable, anonymous per-install identifier for telemetry. Generated once on
 /// first use (128 bits from a cryptographic RNG) and persisted in the secure
 /// keystore, so a device stays a single row across password rotations and FCM
@@ -21,15 +21,9 @@ class TelemetryDeviceId {
       _cached = existing;
       return existing;
     }
-    final generated = _generate();
+    final generated = randomHexId();
     await _storage.write(key: _key, value: generated);
     _cached = generated;
     return generated;
   }
-
-  static String _generate() {
-    final random = Random.secure();
-    final bytes = List<int>.generate(16, (_) => random.nextInt(256));
-    return bytes.map((b) => b.toRadixString(16).padLeft(2, '0')).join();
-  }
 }