{"message":"Shopify Preview & Webhook Service","endpoints":{"preview (text)":"GET /preview?product_id=123&text=NAME&image_url=...&preview_prompt=...","preview (image)":"POST /preview - multipart/form-data with product_image_url, user_image, preview_prompt","images":"GET /images/{previewId}.jpg","webhooks":"POST /webhooks/shopify","health":"GET /health"}}