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.
Per-track high-res datum keyed by EntryKey in the renamed track-waveforms vault; computed at upload for all tracks, regenerable per-track via CMS, with a re-runnable backfill. Mix read path repointed so it keeps working.
Adds ReleaseRepository/ReleaseManager (IReleaseService) for paged medium-filtered
release reads and Session/Mix satellite writes, UnifiedReleaseService orchestrating
vault+SQL, and ReleaseController (5 endpoints). Refactors WaveformProfileService for
configurable bucketCount/vaultName (backward-compatible) and adds the mix-waveforms vault.
Promotes brittle error-string literals to named constants (MixHasNoTrackMessage,
MixTrackNoAudioMessage) on UnifiedReleaseService.
daniel-c-harvey