Add DeliveryTask, Payment, and Sale features

Implemented DeliveryTask, Payment, and Sale entities with full CRUD, business logic, and API endpoints. Updated Order/OrderItem for sale linkage and fulfillment tracking. Registered new DbSets and DI services. Revised documentation for delivery, sale, and payment workflows.

Distribution/Features/Sale/SaleRepository.cs

@@ -0,0 +1,32 @@
+using Distribution.Data;
+using Distribution.Models;
+using Microsoft.EntityFrameworkCore;
+
+namespace Distribution.Features.Sale;
+
+public class SaleRepository(AppDBContext context) : ISaleRepository
+{
+    public async Task<Models.Sale?> GetByIdAsync(Guid id) =>
+        await context.Sales.FindAsync(id);
+
+    public async Task<List<Models.Sale>> GetAllAsync() =>
+        await context.Sales.ToListAsync();
+
+    public async Task<List<Models.Sale>> GetByStoreIdAsync(Guid storeId) =>
+        await context.Sales.Where(s => s.FK_StoreId == storeId && s.IsActive).ToListAsync();
+
+    public async Task AddAsync(Models.Sale sale) =>
+        await context.Sales.AddAsync(sale);
+
+    public void Update(Models.Sale sale) =>
+        context.Sales.Update(sale);
+
+    public void Remove(Models.Sale sale)
+    {
+        sale.IsActive = false;
+        context.Sales.Update(sale);
+    }
+
+    public async Task<Models.Order?> GetOrderBySaleIdAsync(Guid saleId) =>
+        await context.Orders.FirstOrDefaultAsync(o => o.FK_SaleId == saleId && o.IsActive);
+}