Price and free surfaces

One paid endpoint, public discovery for free

Surface	Price	Status
`POST /api/proof/notarize`	`$0.005`	Paid on production mainnet; free in local demo mode.
`/api/capabilities`, `/api/bazaar`, `/api/quickstart`	Free	Discovery endpoints.
`/proof/{id}`, `/api/verify/proofs/{id}`	Free	Verification endpoints.