Fix processing pipeline: report album failures, fault handling on create slips, config key names, audio duration

backend/Core/Musify.Infrastructure/MassTransit/Activities/Audio/TranscodeAudioActivity.cs

@@ -55,7 +55,7 @@ internal class TranscodeAudioActivity(
             var log = new TranscodeAudioLog(workingDirectory);
             return executeContext.CompletedWithVariables(log, new Dictionary<string, object>
             {
-                [RoutingSlipVariableNames.Audio.DurationSeconds] = (int)Math.Round(transcodeResult.Duration.TotalSeconds)
+                [RoutingSlipVariableNames.Audio.DurationSeconds] = transcodeResult.Duration.TotalSeconds
             });
         }
         catch (Exception exception)

backend/Core/Musify.Infrastructure/MassTransit/Activities/Audio/UpdateTrackAudioActivity.cs

@@ -38,11 +38,7 @@ internal class UpdateTrackAudioActivity(
 
         if (string.IsNullOrWhiteSpace(audioFolderKey))
         {
-            logger.LogWarning("Audio folder key is empty for track {TrackId}; skipping update", track.Id);
-            await publishEndpoint.Publish(
-                new TrackAudioProcessed(executeContext.Arguments.TrackId),
-                executeContext.CancellationToken);
-            return executeContext.Completed();
+            throw new InvalidOperationException($"Audio folder key is empty for track {track.Id}");
         }
 
         try