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/TrackEdit.razor

@@ -63,14 +63,7 @@
                               Label="Genre"
                               Variant="Variant.Outlined" />
 
-                <MudSelect @bind-Value="_form.ReleaseType"
-                           Label="Release Type"
-                           Variant="Variant.Outlined">
-                    @foreach (var releaseType in Enum.GetValues<ReleaseType>())
-                    {
-                        <MudSelectItem Value="releaseType">@releaseType</MudSelectItem>
-                    }
-                </MudSelect>
+                <MediumFields @bind-Medium="_form.Medium" @bind-ReleaseType="_form.ReleaseType" Disabled="_busy" />
 
                 <MudNumericField @bind-Value="_form.TrackNumber"
                                  Label="Track Number"
@@ -304,6 +297,10 @@
         public string? ImagePath { get; set; }
         public DateTime? ReleaseDate { get; set; }
         public ReleaseType ReleaseType { get; set; } = ReleaseType.Single;
+
+        // Drives ReleaseType visibility via MediumFields. NOTE: not persisted — PUT api/track/meta has
+        // no medium field, so a medium change on edit is form-shape only until the API grows one.
+        public ReleaseMedium Medium { get; set; } = ReleaseMedium.Cut;
         public int TrackNumber { get; set; } = 1;
 
         public static TrackEditForm From(TrackDto track) => new()
@@ -317,6 +314,7 @@
                 ? d.ToDateTime(TimeOnly.MinValue)
                 : null,
             ReleaseType = track.Release?.ReleaseType ?? ReleaseType.Single,
+            Medium = track.Release?.Medium ?? ReleaseMedium.Cut,
             TrackNumber = track.TrackNumber
         };
     }