CMS Phase 9 Wave 3: Release Archive tab, medium selector, Session/Mix browsers

Renames Genre tab to Release Archive with switch-free medium card group
(Enum.GetValues-driven). Adds MediumFields single dispatch + CutFields/SessionFields/
MixFields per-medium sections embedded by all five upload/edit forms. BatchUpload
enforces single-track invariant for Session/Mix. Adds CmsSessionBrowser (hero-image
upload) and CmsMixBrowser (waveform status + per-row Generate trigger).
ICmsReleaseService/CmsReleaseService wraps api/release endpoints.
Note: medium selector is forward-compat only — API write path pending.

DeepDrftManager/Components/Pages/Tracks/BatchEdit.razor

@@ -34,6 +34,8 @@
                            @bind-Genre="_genre"
                            @bind-ReleaseDate="_releaseDate"
                            @bind-ReleaseType="_releaseType"
+                           Medium="_medium"
+                           MediumChanged="OnMediumChanged"
                            @bind-SelectedImageFile="_selectedImageFile"
                            ExistingImagePath="_existingImagePath"
                            Disabled="_saving" />
@@ -53,6 +55,9 @@
 
         <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. *@
                 <BatchTrackList Tracks="_tracks"
                                 @bind-SelectedIndex="_selectedIndex"
                                 Disabled="_saving"
@@ -124,6 +129,12 @@
     private string _genre = string.Empty;
     private string _releaseDate = string.Empty;
     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.
+    private void OnMediumChanged(ReleaseMedium medium) => _medium = medium;
 
     protected override async Task OnInitializedAsync()
     {
@@ -155,6 +166,7 @@
         _genre = release?.Genre ?? string.Empty;
         _releaseDate = release?.ReleaseDate?.ToString("yyyy-MM-dd") ?? string.Empty;
         _releaseType = release?.ReleaseType ?? ReleaseType.Single;
+        _medium = release?.Medium ?? ReleaseMedium.Cut;
         _existingImagePath = release?.ImagePath;
 
         _tracks = tracks.Select(t => new BatchRowModel