Refactor sales pipeline: ShopPO, Invoice, SysConfig models

Major refactor replacing Sale/Order with ShopPO → Invoice → LoadingSheet flow. Removed legacy Sale/Order models and features; introduced ShopPO, ShopPOItem, Invoice, LoadingSheetOrder, and SysConfig models. Updated related entities, enums, repositories, and controllers. Added new migrations for schema changes and system config. Overhauled business logic and DI registrations. Updated documentation with migration plan.

Distribution/Features/ShopPO/ShopPOService.cs

@@ -0,0 +1,32 @@
+using Distribution.Features.Stock;
+using Distribution.Infra.UoW;
+using Distribution.Models;
+
+namespace Distribution.Features.ShopPO;
+
+public class ShopPOService(
+    IShopPORepository repo,
+    IUnitOfWork uow)
+{
+    private static ShopPOResponse ToResponse(Models.ShopPO p) =>
+        new(p.Id, p.FK_StoreId, p.Store?.StoreName ?? string.Empty,
+            p.RaisedById, p.InvoiceId, p.TotalAmount, p.Status,
+            p.ConfirmedAt, p.ConfirmedBy, p.FulfilledAt,
+            p.Items.Where(i => i.IsActive).Select(i =>
+                new ShopPOItemResponse(i.Id, i.FK_ItemId, i.Item?.Name ?? string.Empty,
+                    i.Quantity, i.QuantityFulfilled, i.UnitPrice, i.IsActive)).ToList(),
+            p.IsActive, p.CreatedAt);
+
+    public async Task<PagedResponse<ShopPOResponse>> GetAllAsync(Guid? agentId, Guid? routeId, Guid? shopId, bool? confirmed, int page, int pageSize)
+    {
+        var total = await repo.GetCountAsync(agentId, routeId, shopId, confirmed);
+        var items = await repo.GetAllAsync(agentId, routeId, shopId, confirmed, page, pageSize);
+        return new PagedResponse<ShopPOResponse>(page, pageSize, total, items.Select(ToResponse).ToList());
+    }
+
+    public async Task<ShopPOResponse?> GetByIdAsync(Guid id)
+    {
+        var po = await repo.GetByIdAsync(id);
+        return po is null ? null : ToResponse(po);
+    }
+}