feat(import): resolve color variety ID mappings mismatch, support unnamed parents in virtual litters, and implement SaleContract updates

GerbilManagerWebAPI/Dtos/ApiDtos.cs

@@ -37,7 +37,7 @@ namespace GerbilManagerWebAPI.Dtos
     public record LitterDto(
         Guid Id,
         string Name,
-        DateOnly Date,
+        DateOnly? Date,
         int? TotalBorn,
         int? DeathsWithin8Weeks,
         Guid? FatherId,
@@ -89,7 +89,7 @@ namespace GerbilManagerWebAPI.Dtos
 
     public record LitterInput(
         string Name,
-        DateOnly Date,
+        DateOnly? Date,
         int? TotalBorn,
         int? DeathsWithin8Weeks,
         Guid? FatherId,

GerbilManagerWebAPI/Dtos/ContractDtos.cs

@@ -19,7 +19,9 @@ namespace GerbilManagerWebAPI.Dtos
         List<Guid> GerbilIds,
         decimal Price,
         DateOnly HandoverDate,
-        DateOnly? ContractDate);
+        DateOnly? ContractDate,
+        // Optionales Tierfoto je Tier (GerbilId -> GerbilPhoto-Id) fürs Vertragsbild.
+        Dictionary<Guid, Guid>? AnimalPhotos = null);
 
     /// <summary>Zuchtprofil — Antwort UND Request-Body von /settings/breeder-profile.</summary>
     public record BreederProfileDto(