feat(p12-w2): track-cardinal high-res waveform fetch + bridge rewire

Add GET api/track/{trackEntryKey}/waveform/high-res (+ proxy), ITrackDataService.GetTrackWaveform; rewire visualizer to resolve the current track's EntryKey and re-fetch on track change. Retire the client mix-waveform read path.

DeepDrftAPI/Services/UnifiedReleaseService.cs

@@ -105,8 +105,9 @@ public class UnifiedReleaseService
     /// <see cref="WaveformResolution"/>), store it in the TrackWaveforms vault under the track's
     /// EntryKey, then point the release's Mix satellite at that same key. The datum key equals the
     /// track's EntryKey — the Mix is single-track. Under the per-track model (phase-12 §5) this is the
-    /// same datum every track now carries; the Mix satellite link is kept so the existing public
-    /// <c>GET api/release/{entryKey}/mix/waveform</c> read path keeps resolving until 12.B2 rewires it.
+    /// same datum every track now carries. The visualizer fetches it via the track-cardinal
+    /// <c>GET api/track/{trackEntryKey}/waveform/high-res</c> (12.B2); the Mix satellite link and the
+    /// legacy release-addressed read path are retained transitionally and no longer feed the visualizer.
     /// </summary>
     public async Task<Result> TriggerMixWaveformAsync(long releaseId, CancellationToken ct)
     {