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/Genetics/InbreedingResult.cs

@@ -0,0 +1,25 @@
+namespace GerbilManagerWebAPI.Genetics
+{
+    /// <summary>
+    /// Result of an inbreeding-coefficient (Inzuchtkoeffizient) calculation for an
+    /// individual or a hypothetical pairing.
+    /// </summary>
+    /// <param name="Coefficient">Wright's inbreeding coefficient F, in the range 0..1.</param>
+    /// <param name="Percent">The coefficient expressed as a percentage (F * 100).</param>
+    /// <param name="GenerationsAvailable">
+    /// The deepest generation of known ancestry above the individual (parents = 1,
+    /// grandparents = 2, …). 0 when no parents are recorded.
+    /// </param>
+    /// <param name="CommonAncestors">
+    /// The ancestors common to both parents, each with its additive contribution to F,
+    /// ordered by contribution descending. Empty when there is no inbreeding.
+    /// </param>
+    public record InbreedingResult(
+        double Coefficient,
+        double Percent,
+        int GenerationsAvailable,
+        IReadOnlyList<CommonAncestorContribution> CommonAncestors);
+
+    /// <summary>A single common ancestor and how much it contributes to F.</summary>
+    public record CommonAncestorContribution(Guid Id, string Name, double Contribution);
+}