feat: normalize release-cardinal fields out of track into a Release entity (Phase 8 §8.0)

DeepDrftModels/Entities/ReleaseEntity.cs

@@ -0,0 +1,23 @@
+using DeepDrftModels.Enums;
+using Models.Entities;
+
+namespace DeepDrftModels.Entities;
+
+// The release-cardinal half of the normalized track schema (Phase 8 §8.0). One ReleaseEntity is
+// shared by every track on the same album; track-cardinal data stays on TrackEntity, which points
+// back here via a nullable ReleaseId (singles and loose tracks have no release context).
+//
+// Inherits Id, CreatedAt, UpdatedAt, IsDeleted from BaseEntity (Cerebellum.BlazorBlocks.Models).
+// BaseEntity ships the audit columns but does not declare IEntity itself, so subclasses declare it
+// explicitly to satisfy the generic constraints on Repository<>/Manager<>/etc.
+public class ReleaseEntity : BaseEntity, IEntity
+{
+    public required string Title { get; set; }
+    public required string Artist { get; set; }
+    public string? Genre { get; set; }
+    public DateOnly? ReleaseDate { get; set; }
+    public string? ImagePath { get; set; }
+    public ReleaseType ReleaseType { get; set; } = ReleaseType.Single;
+    public long? CreatedByUserId { get; set; }
+    public ICollection<TrackEntity> Tracks { get; set; } = new List<TrackEntity>();
+}