DATA-2: new schema entities + Minimal API endpoints + Scalar + DAL teardown

- Entities: Breeder->Contact, +Enclosure/ColorVariety/GerbilPhoto/HealthRecord/WeightRecord;
  Gerbil expanded (single Genotype text col, Status/Gender enums-as-string, FK ids,
  ImportSource/ExternalRef provenance); Litter Strength->TotalBorn +ExpectedGoHomeDate/Notes.
  ColorVariety HasData seed = 18 from GEN-1 catalog. Gerbil<->Litter cycle handled
  (SetNull/Restrict). Enums stored as strings.
- Minimal API (no controllers): Endpoints/*.cs MapGroup+TypedResults for gerbils, litters,
  contacts, enclosures, color-varieties, health/weight-records, inbreeding (converted from
  controller, same routes/shapes), photos (Oscar contract: GET array/POST multipart/DELETE,
  url /photos/files/{fileName}). Gridify paged {items,totalCount,page,pageSize}, camelCase,
  409 conflict-deletes, flat FK ids, litter parent-gender validation (400 {code,...}).
- Scalar replaces Swashbuckle (AddOpenApi/MapOpenApi + MapScalarApiReference at /scalar);
  launchUrl swagger->scalar. GenericRepository/UnitOfWork/Converters deleted; DbContext direct.
- InbreedingService reads real FK props now; pure calculator + 8 tests untouched.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

GerbilManagerWebAPI/Models/Litter.cs

@@ -2,15 +2,24 @@ using System.ComponentModel.DataAnnotations;
 
 namespace GerbilManagerWebAPI.Models
 {
-    public record Litter
+    /// <summary>A litter (Wurf). Parents are gerbils; juveniles are Gerbils linked via Gerbil.LitterId.</summary>
+    public class Litter
     {
         [Key]
-        public Guid Id { get; init; }
+        public Guid Id { get; set; }
         public required string Name { get; set; }
-        public required DateTime Date { get; set; }
-        public int? Strength { get; set; }
+        public DateOnly Date { get; set; }
+
+        /// <summary>Total born count (was "Strength").</summary>
+        public int? TotalBorn { get; set; }
+
+        public Guid? FatherId { get; set; }
         public Gerbil? Father { get; set; }
+        public Guid? MotherId { get; set; }
         public Gerbil? Mother { get; set; }
+
+        /// <summary>Computed ~35 days after Date by default; editable.</summary>
+        public DateOnly? ExpectedGoHomeDate { get; set; }
+        public string? Notes { get; set; }
     }
 }
-