feat: add salePrice field to Product model and update related files

- Added salePrice field to Product model in Prisma schema and generated files.
- Updated Product scalar field enums in both TypeScript files.
- Modified aggregate output types to include salePrice.
- Enhanced input types for creating and updating products to support salePrice.
- Updated migration file to add salePrice column to Products table.
- Created DTOs for inventory management in POS module.
- Implemented POS controller and service with methods for stock and product categories.

src/pos/pos.module.ts

@@ -0,0 +1,11 @@
+import { Module } from '@nestjs/common'
+import { PrismaModule } from '../prisma/prisma.module'
+import { PosController } from './pos.controller'
+import { PosService } from './pos.service'
+
+@Module({
+  imports: [PrismaModule],
+  controllers: [PosController],
+  providers: [PosService],
+})
+export class PosModule {}