Create Product Controller

Holds the form state and runs the multi-call submit: upload images via VendorService.uploadPublicFile, build the create payload, POST /vendor/products, then attach the inventory rows via setInventoryItemQuantity + assignInventoryItemLocations + addProductLocation.

1. setTitle / setDescription / setImageFiles / pickCategory mutate state.
2. addOption / addOptionValue / removeOption rebuild the variants matrix.
3. submit: uploadPublicFile per image → createPhysicalProduct → assignInventoryItemLocations + setInventoryItemQuantity per variant.
4. Errors short-circuit and surface in state.submitError.

• Image upload is sequential — parallelizing would speed up but the backend rate-limits /vendor/files.
• Variant inventory is set as an after-creation step; if it fails, the product exists but with 0 stock.
• Currency is per-product (not per-variant) — Medusa supports per-variant but the UI simplifies.

• lib/src/features/seller/products/providers/create_product_provider.dart
• lib/src/core/services/vendor_service.dart:230 // createPhysicalProduct
• lib/src/core/services/vendor_service.dart:403 // assignInventoryItemLocations
• lib/src/core/services/vendor_service.dart:423 // setInventoryItemQuantity

Same multi-call pattern as the provision wizard — if you change one, evaluate the other for consistency.