GoodWidget backend API gaps

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Motivation

GoodWidget needs Worker APIs beyond credit ingestion: users should see history and funding status, onboard the AntSeed buyer operator, withdraw principal, and manage payment channels.
Chain reads and EIP-712 signing payloads are handled in the UI via direct RPC calls. The Worker exposes KV-backed reads and on-chain write/submit endpoints only.

Details

History — Paginated credit/transaction list from KV (gdCredits), with optional filters for funding status.

Operator onboarding — EIP-712 consent flow so the buyer accepts AntseedBuyerOperator on Base before deposits are funded.

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Updated the Worker API to match the read-vs-write split: removed GET routes that only proxied Base/Celo chain reads or built signing payloads; the UI reads those directly from chain.
Originally I had tried to keep the UI off Base chain reads

Removed: quote endpoints, account status, operator read/consent-payload, withdrawable, withdraw/payload.