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/MixFields.razor

@@ -0,0 +1,10 @@
+@* Mix-medium fields. The high-res waveform is a server-side derived datum: the CMS fires a body-less
+   trigger (POST api/release/{id}/mix/waveform) after the release exists, so generation is managed
+   per-row in the Mixes browser, not at create time. On upload the trigger is fired automatically; this
+   section states that contract and carries no input of its own. *@
+<MudItem xs="12">
+    <MudAlert Severity="Severity.Info" Dense="true" Variant="Variant.Outlined">
+        Mixes are single-track DJ releases. The high-resolution waveform is generated automatically
+        after upload; regenerate it any time from the <strong>Release Archive → Mixes</strong> browser.
+    </MudAlert>
+</MudItem>