feat(ruecknahmen): zurückgenommene Tiere erfassen

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

GerbilManagerWebAPI/Dtos/ReturnRecordDtos.cs

@@ -0,0 +1,28 @@
+namespace GerbilManagerWebAPI.Dtos
+{
+    /// <summary>RÜCKNAHME: Payload für POST/PUT /returns.</summary>
+    public record ReturnRecordInput(
+        Guid? GerbilId,
+        string? GerbilName,
+        DateTime? ReturnDate,
+        decimal? ReturnPrice,
+        decimal? OriginalPrice,
+        DateTime? OriginalSaleDate,
+        Guid? FromContactId,
+        string? FromContactName,
+        string? Note);
+
+    /// <summary>RÜCKNAHME: Antwort-DTO für einen gespeicherten Rücknahme-Datensatz.</summary>
+    public record ReturnRecordDto(
+        Guid Id,
+        Guid? GerbilId,
+        string? GerbilName,
+        DateTime? ReturnDate,
+        decimal? ReturnPrice,
+        decimal? OriginalPrice,
+        DateTime? OriginalSaleDate,
+        Guid? FromContactId,
+        string? FromContactName,
+        string? Note,
+        DateTimeOffset CreatedAt);
+}