fix(downloads): hide unknown byte totals in notifications

lib/providers/download_queue_provider_progress.dart

@@ -373,8 +373,11 @@ extension _DownloadQueueProgress on DownloadQueueNotifier {
           notifProgress = 0;
           notifTotal = 0;
         } else if (bytesTotal <= 0) {
-          notifProgress = (progressPercent * 100).toInt();
-          notifTotal = 100;
+          notifTotal = PlatformBridge.notificationPercentTotal;
+          notifProgress = (progressPercent * notifTotal)
+              .round()
+              .clamp(0, notifTotal)
+              .toInt();
         }
         final serviceStatus = notifTotal <= 0 ? 'preparing' : 'downloading';
 

lib/services/platform_bridge.dart

@@ -145,6 +145,10 @@ class _BridgeInFlight<T> {
 }
 
 class PlatformBridge {
+  /// Sentinel shared with Android's foreground service for progress reports
+  /// that contain a percentage but no byte counts.
+  static const int notificationPercentTotal = 10000;
+
   static const _channel = MethodChannel('com.zarz.spotiflac/backend');
   static const _jsonResultFileKey = '__json_file';
   static const _backgroundJsonDecodeThresholdBytes = 128 * 1024;