feat(ausstellungen): Ausstellungs-/Auszeichnungsergebnisse je Tier

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

GerbilManagerWebAPI/Models/ExhibitionResult.cs

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+using System.ComponentModel.DataAnnotations;
+
+namespace GerbilManagerWebAPI.Models
+{
+    /// <summary>
+    /// EXHIBITION: a show/exhibition result or award for an animal (RennmausPro `ausz_tb` +
+    /// `_AUSZ` flag — present in RPRO3 but unused by this breeder; implemented fully anyway).
+    ///
+    /// Deliberately decoupled from the rest of the model, exactly like <see cref="Feedback"/>:
+    /// GerbilId is a plain nullable Guid column (NOT an enforced foreign key, no navigation
+    /// property), so the import re-ingest wipe (IngestResolvedService) can delete/recreate
+    /// gerbils without deleting or breaking exhibition rows. Captured EntityName keeps the
+    /// record human-readable even after the referenced animal is gone.
+    /// </summary>
+    public class ExhibitionResult
+    {
+        [Key]
+        public Guid Id { get; set; }
+
+        /// <summary>Loose reference (no FK) to the gerbil this result belongs to, if any.</summary>
+        public Guid? GerbilId { get; set; }
+
+        /// <summary>Captured name of the referenced animal (survives an ingest wipe).</summary>
+        public string? EntityName { get; set; }
+
+        /// <summary>Name of the show/event (Veranstaltung), e.g. "Nationale Rennmausschau 2026".</summary>
+        public required string EventName { get; set; }
+
+        /// <summary>Date of the event, if known.</summary>
+        public DateTime? Date { get; set; }
+
+        /// <summary>Placement / ranking, e.g. "1. Platz", "BOB".</summary>
+        public string? Placement { get; set; }
+
+        /// <summary>Award / title (Auszeichnung), e.g. "Best in Show", "V1".</summary>
+        public string? Award { get; set; }
+
+        /// <summary>Free-text note (Bewertung / Bemerkung).</summary>
+        public string? Note { get; set; }
+
+        /// <summary>Server-side creation time.</summary>
+        public DateTimeOffset CreatedAt { get; set; }
+    }
+}