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.

DeepDrftPublic.Client/Services/ITrackDataService.cs

@@ -30,6 +30,14 @@ public interface ITrackDataService
 
     Task<ApiResult<TrackDto>> GetTrack(string trackId);
 
+    /// <summary>
+    /// The per-track high-res waveform datum, addressed by the track's EntryKey (phase-12 §5b — the
+    /// datum is the track's; the release is only addressing context). Success with a value when a
+    /// high-res datum is stored; success with a null value when none is (a not-yet-backfilled track —
+    /// a valid state, not a failure, the visualizer blanks); failure on any other transport error.
+    /// </summary>
+    Task<ApiResult<WaveformProfileDto?>> GetTrackWaveform(string trackEntryKey);
+
     /// <summary>
     /// Fetches a random track from the public library for instant play. Success with a value on a
     /// hit; success with a null value when the library is empty (a valid state, not a failure);