Add track publication, album types, optional track pictures and batch upload URLs

Tracks
- Track.IsPublished (migration marks existing tracks as published). New
  tracks are created unpublished.
- PUT /tracks/{id}/published and PUT /tracks/published change the flag;
  publishing requires completed audio processing (the batch endpoint
  reports skipped tracks).
- An unpublished track is only visible to its owner. A WherePublished /
  VisibleTo filter is applied to search, genres, listening history, last
  listened, likes, mixes, album and playlist contents and counts, recently
  listened albums, public user tracks, track details and stream tickets.
- isPublished is part of the track responses, GET /tracks/users/{userId}
  accepts a published filter and status-counts reports published and
  unpublished totals.
- CreateTrackRequest.pictureIntentId is optional: without it the track
  uses the album cover or the preset picture and no picture processing
  runs. CreateTrackResourcesEvent carries nullable picture fields, so
  queues must be drained before deploying.
- POST /tracks/upload-urls accepts an audios list and one optional picture
  shared by all of them, and returns an intent per file. The upload intent
  limits are raised so a batch fits.

Albums
- AlbumType (Album, EP, Single) on create, update and responses.
- CreateAlbumRequest.trackIds creates the album and links the tracks in a
  single save.

backend/Tests/Musify.Infrastructure.Tests/MassTransit/RoutingSlipBuilderTests.cs

@@ -88,6 +88,43 @@ namespace Musify.Infrastructure.Tests.MassTransit
             AssertPictureSourceSlip(slip, RoutingSlipVariableNames.ProcessKinds.PlayListPicture, ActivityNames.PublishPlayListPictureProcessingEvent);
         }
 
+        [Fact]
+        public void CreateTrack_WithPicture_CopiesBothFilesAndConsumesBothIntents()
+        {
+            var audioIntentId = Guid.NewGuid();
+            var message = new CreateTrackResourcesEvent(
+                SubjectId, IntentId, audioIntentId, "bucket", "picture-source", "picture-final", "audio-source", "audio-final", "audio-folder", Sizes);
+
+            var slip = new CreateTrackRoutingSlipBuilder().Build(message, CorrelationId).Build();
+
+            Assert.Equal(
+                [ActivityNames.CopyPictureToFinal, ActivityNames.CopyAudioToFinal, ActivityNames.ConsumeUploadIntents, ActivityNames.PublishTrackProcessingEvents],
+                slip.Itinerary.Select(activity => activity.Name));
+            Assert.Equal("picture-final", slip.Variables[RoutingSlipVariableNames.Workflow.PictureKey]);
+            var consume = new Dictionary<string, object>(slip.Itinerary[2].Arguments, StringComparer.OrdinalIgnoreCase);
+            Assert.Equal([IntentId, audioIntentId], (IEnumerable<Guid>)consume["IntentIds"]);
+        }
+
+        [Fact]
+        public void CreateTrack_WithoutPicture_SkipsThePictureCopyAndOnlyConsumesTheAudioIntent()
+        {
+            var audioIntentId = Guid.NewGuid();
+            var message = new CreateTrackResourcesEvent(
+                SubjectId, null, audioIntentId, "bucket", null, null, "audio-source", "audio-final", "audio-folder", Sizes);
+
+            var slip = new CreateTrackRoutingSlipBuilder().Build(message, CorrelationId).Build();
+
+            Assert.Equal(
+                [ActivityNames.CopyAudioToFinal, ActivityNames.ConsumeUploadIntents, ActivityNames.PublishTrackProcessingEvents],
+                slip.Itinerary.Select(activity => activity.Name));
+            Assert.False(slip.Variables.ContainsKey(RoutingSlipVariableNames.Workflow.PictureKey));
+            Assert.Equal("audio-final", slip.Variables[RoutingSlipVariableNames.Workflow.AudioKey]);
+            var consume = new Dictionary<string, object>(slip.Itinerary[1].Arguments, StringComparer.OrdinalIgnoreCase);
+            Assert.Equal([audioIntentId], (IEnumerable<Guid>)consume["IntentIds"]);
+            var publish = new Dictionary<string, object>(slip.Itinerary[2].Arguments, StringComparer.OrdinalIgnoreCase);
+            Assert.Null(publish["FinalPictureKey"]);
+        }
+
         [Fact]
         public void AudioWorkflow_ChainsDownloadTranscodeTransferAndUpdate()
         {