feat(BE-48): auto-create product_warehouse on stock adjustment & remove unused APIs

- Change logic: automatically create product_warehouse if it does not exist during stock adjustment
- Remove unnecessary/unused API endpoints
- Ensure adjustment process continues even if product_warehouse was not previously available

internal/modules/inventory/product-warehouses/repositories/product_warehouse.repository.go

@@ -13,6 +13,7 @@ type ProductWarehouseRepository interface {
 	ProductWarehouseExists(ctx context.Context, productId, warehouseId uint, excludeID *uint) (bool, error)
 	IsProductExist(ctx context.Context, productId uint) (bool, error)
 	IsWarehouseExist(ctx context.Context, warehouseId uint) (bool, error)
+	ProductWarehouseExistByProductAndWarehouseID(ctx context.Context, productId, warehouseId uint) (bool, error)
 	ExistsByID(ctx context.Context, id uint) (bool, error)
 	GetProductWarehouseByProductAndWarehouseID(ctx context.Context, productId, warehouseId uint) (*entity.ProductWarehouse, error)
 }
@@ -53,6 +54,17 @@ func (r *ProductWarehouseRepositoryImpl) ExistsByID(ctx context.Context, id uint
 	return repository.Exists[entity.ProductWarehouse](ctx, r.db, id)
 }
 
+func (r *ProductWarehouseRepositoryImpl) ProductWarehouseExistByProductAndWarehouseID(ctx context.Context, productId, warehouseId uint) (bool, error) {
+	var count int64
+	if err := r.db.WithContext(ctx).
+		Model(&entity.ProductWarehouse{}).
+		Where("product_id = ? AND warehouse_id = ?", productId, warehouseId).
+		Count(&count).Error; err != nil {
+		return false, err
+	}
+	return count > 0, nil
+}
+
 func (r *ProductWarehouseRepositoryImpl) GetProductWarehouseByProductAndWarehouseID(ctx context.Context, productId, warehouseId uint) (*entity.ProductWarehouse, error) {
 	var productWarehouse entity.ProductWarehouse
 	if err := r.DB().WithContext(ctx).Where("product_id = ? AND warehouse_id = ?", productId, warehouseId).First(&productWarehouse).Error; err != nil {