Add inventory management features including Sales, Stock Returns, and Suppliers

- Implement Sale and SaleItem models for tracking sales transactions.
- Create StockReturn model to manage stock adjustments for various reasons.
- Introduce Supplier model to represent suppliers of products.
- Develop InventoryRepository for CRUD operations on products, suppliers, sales, and stock returns.
- Implement InventoryService to handle business logic for inventory management.
- Update TenantDbContext to include new models and relationships.
- Enhance ProfitLossRepository to account for sales, purchases, and stock returns in profit and loss calculations.
- Modify Program.cs to register new inventory-related services.

Program.cs

@@ -142,6 +142,7 @@ builder.Services.AddScoped<IPlatformBillingRepository, PlatformBillingRepository
 builder.Services.AddScoped<ICustomerNotificationRepository, CustomerNotificationRepository>();
 builder.Services.AddScoped<IFacilityRepository, FacilityRepository>();
 builder.Services.AddScoped<IBookingRepository, BookingRepository>();
+builder.Services.AddScoped<IInventoryRepository, InventoryRepository>();
 builder.Services.AddScoped<ITimeBankCardRepository, TimeBankCardRepository>();
 builder.Services.AddScoped<IRfidTagRepository, RfidTagRepository>();
 
@@ -163,6 +164,7 @@ builder.Services.AddScoped<ICustomerInvoiceService, CustomerInvoiceService>();
 builder.Services.AddScoped<ICustomerSubscriptionService, CustomerSubscriptionService>();
 builder.Services.AddScoped<IFacilityService, FacilityService>();
 builder.Services.AddScoped<IBookingService, BookingService>();
+builder.Services.AddScoped<IInventoryService, InventoryService>();
 builder.Services.AddScoped<IRfidTagService, RfidTagService>();
 builder.Services.AddScoped<ITimeBankCardService, TimeBankCardService>();
 builder.Services.AddScoped<IBootstrapService, BootstrapService>();