Add pricing and supplier master data

Distribution/Features/PriceList/PriceListDTOs.cs

@@ -0,0 +1,25 @@
+namespace Distribution.Features.PriceList;
+
+public record CreatePriceListRequest(string Name, Guid? RegionId, DateTime EffectiveFrom, DateTime EffectiveTo);
+
+public record UpdatePriceListRequest(string Name, Guid? RegionId, DateTime EffectiveFrom, DateTime EffectiveTo);
+
+public record UpsertPriceListItemRequest(decimal Price, decimal? MinPrice = null);
+
+public record PriceListItemResponse(Guid Id, Guid ItemId, string Sku, string ItemName, decimal Price, decimal? MinPrice);
+
+/// <summary>
+/// A resolved price with its negotiable floor. MinPrice null = no negotiation, Price is fixed.
+/// </summary>
+public record PriceResolution(decimal Price, decimal? MinPrice);
+
+public record PriceListResponse(
+    Guid Id,
+    string Name,
+    Guid? RegionId,
+    string? RegionName,
+    DateTime EffectiveFrom,
+    DateTime EffectiveTo,
+    bool IsActive,
+    DateTime CreatedAt,
+    List<PriceListItemResponse> Items);