Catalog and inventory

• GET, POST /storefront/categories/; GET, PATCH, PUT, DELETE /storefront/categories/{id}/: merchant categories.
• GET, POST /storefront/products/; GET, PATCH, PUT, DELETE /storefront/products/{id}/: merchant products.
• POST /storefront/products/{id}/upload-image/: product image upload.
• GET, POST /inventory/warehouses/; detail routes: merchant warehouses.
• GET /inventory/stock-levels/: stock by warehouse and product.
• POST /inventory/stock-levels/{id}/adjust/: audited adjustment.
• POST /inventory/stock-levels/transfer/: atomic warehouse transfer.
• GET /inventory/stock-movements/: movement history.

Create stock levels at zero, then use the adjustment and transfer actions so every quantity change has a movement record. Quantity, reserved stock and stock-level identity cannot be patched directly. A level or warehouse with stock history cannot be deleted. Product availability depends on its inventory tracking setting; a product with tracking disabled is not automatically sold out at zero stock.