FEAT-1b: Inzuchtkoeffizient endpoints via Wright path method

- PedigreeCalculator: pure, EF-free Wright path-method engine (recursive F_A,
  per-common-ancestor contributions, generationsAvailable, cycle guards)
- InbreedingService: loads pedigree from ApplicationContext shadow FKs
  (Gerbils.LitterId, Litters.FatherId/MotherId) into in-memory maps
- InbreedingController: GET /gerbils/{id}/inbreeding-coefficient,
  POST /genetics/test-inbreeding (hypothetical pairing for Probeverpaarung)
- Injects ApplicationContext directly; no Program.cs change (Dwight owns it)

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

GerbilManagerWebAPI/Controllers/InbreedingController.cs

@@ -0,0 +1,39 @@
+using GerbilManagerWebAPI.DAL;
+using GerbilManagerWebAPI.Dtos;
+using GerbilManagerWebAPI.Genetics;
+using Microsoft.AspNetCore.Mvc;
+
+namespace GerbilManagerWebAPI.Controllers
+{
+    /// <summary>
+    /// Inbreeding-coefficient (Inzuchtkoeffizient) endpoints — both for an existing
+    /// gerbil and for a hypothetical pairing (Probeverpaarung).
+    /// </summary>
+    [ApiController]
+    public class InbreedingController : ControllerBase
+    {
+        private readonly InbreedingService service;
+
+        // ApplicationContext is already registered in DI; the service is a thin,
+        // dependency-free wrapper so it needs no separate registration in Program.cs.
+        public InbreedingController(ApplicationContext db)
+        {
+            service = new InbreedingService(db);
+        }
+
+        // GET /gerbils/{id}/inbreeding-coefficient
+        [HttpGet("gerbils/{id}/inbreeding-coefficient")]
+        public ActionResult<InbreedingResult> GetForGerbil(Guid id)
+        {
+            var result = service.ForGerbil(id);
+            return result is null ? NotFound() : result;
+        }
+
+        // POST /genetics/test-inbreeding
+        [HttpPost("genetics/test-inbreeding")]
+        public ActionResult<InbreedingResult> TestPairing(TestInbreedingDto dto)
+        {
+            return service.ForPairing(dto.FatherId, dto.MotherId);
+        }
+    }
+}