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/GerbilPhoto.cs

@@ -0,0 +1,17 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace GerbilManagerWebAPI.Models
+{
+    /// <summary>A photo of a gerbil. The file lives under a configured FS root; only the
+    /// file name is stored in the DB. The first photo by SortOrder is the profile photo.</summary>
+    public class GerbilPhoto
+    {
+        [Key]
+        public Guid Id { get; set; }
+        public Guid GerbilId { get; set; }
+        public required string FileName { get; set; }
+        public string? Caption { get; set; }
+        public int SortOrder { get; set; }
+        public DateTimeOffset CreatedAt { get; set; }
+    }
+}