Phase 9 Wave 2: api/release endpoint family — medium-aware reads + metadata writes

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.

DeepDrftData/IReleaseService.cs

@@ -0,0 +1,31 @@
+using DeepDrftModels.DTOs;
+using DeepDrftModels.Enums;
+using Models.Common;
+using NetBlocks.Models;
+
+namespace DeepDrftData;
+
+/// <summary>
+/// SQL-side release service. Repository outputs entities; this service outputs DTOs via TrackConverter.
+/// Backs the medium-aware release read endpoints (paged list + by-id detail) and the two metadata
+/// write paths (Session hero image, Mix waveform). The entity never escapes the service layer.
+/// </summary>
+public interface IReleaseService
+{
+    /// <summary>Paginated releases, optionally filtered to one medium. The matching medium's metadata satellite is included in the result. Omit medium for all releases.</summary>
+    Task<ResultContainer<PagedResult<ReleaseDto>>> GetPagedAsync(
+        int page, int pageSize, string? sortColumn, bool sortDescending,
+        ReleaseMedium? medium, CancellationToken cancellationToken = default);
+
+    /// <summary>Single release with both metadata navs included (nulls for non-matching media).</summary>
+    Task<ResultContainer<ReleaseDto?>> GetByIdAsync(long id, CancellationToken cancellationToken = default);
+
+    /// <summary>Track entry keys for a release. Single-entry for Session/Mix (enforced at upload); may be multiple for Cut.</summary>
+    Task<ResultContainer<List<string>>> GetTrackEntryKeysAsync(long releaseId, CancellationToken cancellationToken = default);
+
+    /// <summary>Find-or-create the Session satellite and set its hero image entry key. Fails when the release is not a Session.</summary>
+    Task<Result> SetSessionHeroImageAsync(long releaseId, string heroImageEntryKey, CancellationToken cancellationToken = default);
+
+    /// <summary>Find-or-create the Mix satellite and set its waveform entry key. Fails when the release is not a Mix.</summary>
+    Task<Result> SetMixWaveformAsync(long releaseId, string waveformEntryKey, CancellationToken cancellationToken = default);
+}