Make release Medium writable via upload + meta-edit; resolve detail-page track by releaseId not album title

DeepDrftManager/Components/Pages/Tracks/BatchEdit.razor

@@ -55,9 +55,10 @@
 
         <MudGrid>
             <MudItem xs="12" md="5">
-                @* TODO: When medium write path lands, collapse to single-track slot here for Session/Mix
-                   (matching BatchUpload's @if (_medium == ReleaseMedium.Cut) guard). Until then,
-                   BatchEdit's track list is unrestricted because _medium is read-only on the edit form. *@
+                @* The medium write path persists _medium on save (9.5.B). BatchEdit still shows the full
+                   multi-track list for every medium; collapsing to a single-track slot for Session/Mix
+                   (matching BatchUpload's @if (_medium == ReleaseMedium.Cut) guard) is deferred form-shape
+                   work, not part of the write-path wiring. *@
                 <BatchTrackList Tracks="_tracks"
                                 @bind-SelectedIndex="_selectedIndex"
                                 Disabled="_saving"
@@ -131,9 +132,9 @@
     private ReleaseType _releaseType = ReleaseType.Single;
     private ReleaseMedium _medium = ReleaseMedium.Cut;
 
-    // The medium selector drives ReleaseType visibility. NOTE: the metadata update endpoint
-    // (PUT api/track/meta) has no medium field, so a medium change is not persisted on save today —
-    // the selector reflects/adjusts local form shape only. Persisting medium-on-edit is an API change.
+    // The medium selector drives ReleaseType visibility and is persisted on save: every UpdateAsync /
+    // UploadTrackAsync call below passes _medium, and PUT api/track/meta resets ReleaseType to its
+    // default server-side for a non-Cut medium.
     private void OnMediumChanged(ReleaseMedium medium) => _medium = medium;
 
     protected override async Task OnInitializedAsync()
@@ -373,6 +374,7 @@
                             releaseDate,
                             imagePathForUpdate,
                             _releaseType,
+                            _medium,
                             trackNumber);
 
                         if (!updateResult.Success)
@@ -407,7 +409,8 @@
                             row.WavFile.Name,
                             createdByUserId,
                             _releaseType,
-                            trackNumber);
+                            trackNumber,
+                            _medium);
 
                         if (!uploadResult.Success || uploadResult.Value is null)
                         {
@@ -433,6 +436,7 @@
                                     releaseDate,
                                     linkPath,
                                     _releaseType,
+                                    _medium,
                                     trackNumber);
 
                                 if (!linkResult.Success)