feat(data): add navigation properties to all entity models

src/ClaudeDo.Data/Models/WorktreeEntity.cs

@@ -18,4 +18,7 @@ public sealed class WorktreeEntity
     public string? DiffStat { get; set; }
     public WorktreeState State { get; set; } = WorktreeState.Active;
     public required DateTime CreatedAt { get; init; }
+
+    // Navigation property
+    public TaskEntity Task { get; set; } = null!;
 }