PASS  GET  /api/products                      -> 200  {"count":6,"items":[{"sku":"SKU-2001","name":"Bin liners 50L","category":"Cleaning","qty":120},{"sku":"SKU-200   (List all products)
PASS  GET  /api/products?category=Garden      -> 200  {"count":2,"items":[{"sku":"SKU-2002","name":"Hose nozzle","category":"Garden","qty":35},{"sku":"SKU-2006","na   (Filter by category)
PASS  GET  /api/products/SKU-2004             -> 200  {"sku":"SKU-2004","name":"Chef knife 20cm","category":"Kitchen","qty":9}   (One product)
PASS  GET  /api/products/SKU-9999             -> 404  {"error":"Unknown SKU"}   (Unknown SKU)
PASS  POST /api/stock/adjust                  -> 401  {"error":"Missing or wrong API key"}   (Adjust without key)
PASS  POST /api/stock/adjust                  -> 200  {"sku":"SKU-2004","on_hand":7}   (Adjust down)
PASS  POST /api/stock/adjust                  -> 409  {"error":"Stock cannot go below zero","on_hand":7}   (Stock below zero refused)
PASS  POST /api/stock/adjust                  -> 422  {"error":"A reason is required"}   (Missing reason)
PASS  POST /api/stock/adjust                  -> 422  {"error":"Send sku and a non-zero whole-number delta"}   (Text delta refused)
PASS  POST /api/stock/adjust                  -> 200  {"sku":"SKU-2006","on_hand":24}   (Restock)
PASS  GET  /api/products?category=Garden      -> 200  {"count":2,"items":[{"sku":"SKU-2002","name":"Hose nozzle","category":"Garden","qty":35},{"sku":"SKU-2006","na   (Restock visible in list)
PASS  GET  /api/orders                        -> 404  {"error":"Not found"}   (Unknown route)

12 of 12 API tests passed