Multi-profile resolution shipped in :52 but nothing wrote
products.merchant_profile_id, so it was non-functional end to end.
Add merchant_profile_id to the Product model + all four product
SELECTs, a set_product_merchant_profile writer (validates the target
profile exists, returning 404 instead of a raw FK-violation 500), and
thread an optional field through CreateProductReq (post-write) and
UpdateProductReq (double-Option; Some(None) clears to default). The
admin SPA product form shows a profile picker only when >1 profile
exists. Mirrors the entitlements-catalog post-write pattern.
Tests: repo round-trip (attach/resolve/clear/bad-id) + HTTP handler
arms. api suite 54→56, full suite green.
Grant
b088bfc062