Add products and sales management modules with database schema and validation

- Introduced `ProductsModule` to manage product data, including read and write controllers.
- Created database migrations for the `products`, `sales_requests`, `sales_orders`, `sales_invoices`, and related tables, including constraints and unique indexes.
- Implemented validation for product fields such as code, name, unit, and brand with corresponding utility functions.
- Developed service and repository layers for handling product and sales data operations.
- Added unit tests for the products and sales services, repositories, and controllers to ensure functionality and correctness.
- Updated application module to include the new `ProductsModule` and related sales modules for better organization.

src/app.module.ts

@@ -6,6 +6,7 @@ import loadEnv from './config/env';
 import { DatabaseModule } from './database/database.module';
 import { AuthModule } from './modules/auth/auth.module';
 import { ConfigurationModule } from './modules/configuration/configuration.module';
+import { SalesModule } from './modules/sales/sales.module';
 import { PrivilegesModule } from './modules/privileges/privileges.module';
 import { UsersModule } from './modules/users/users.module';
 
@@ -20,6 +21,7 @@ import { UsersModule } from './modules/users/users.module';
     AuthModule,
     PrivilegesModule,
     ConfigurationModule,
+    SalesModule,
   ],
   controllers: [AppController],
   providers: [AppService],