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/Services/CmsTrackService.cs

@@ -44,6 +44,7 @@ public class CmsTrackService : ICmsTrackService
         long createdByUserId,
         ReleaseType releaseType,
         int trackNumber,
+        ReleaseMedium medium = ReleaseMedium.Cut,
         CancellationToken ct = default)
     {
         // Rebuild the multipart container so the boundary is owned by HttpClient and the
@@ -63,6 +64,9 @@ public class CmsTrackService : ICmsTrackService
         multipart.Add(new StringContent(createdByUserId.ToString()), "createdByUserId");
         multipart.Add(new StringContent(releaseType.ToString()), "releaseType");
         multipart.Add(new StringContent(trackNumber.ToString()), "trackNumber");
+        // Forward-compatible: the upload endpoint does not bind a "medium" field yet (server defaults
+        // to Cut). Sent so the value round-trips once the API grows the parameter; ignored until then.
+        multipart.Add(new StringContent(medium.ToString()), "medium");
 
         var client = _httpClientFactory.CreateClient(ContentCmsClientName);
         using var request = new HttpRequestMessage(HttpMethod.Post, UploadPath) { Content = multipart };