Get sandbox bank frontend config

Returns the deterministic sandbox bank frontend configuration when the authenticated automation client has banks.frontends.read. External URL: /v1/banks/current/frontend-config. Current Next.js implementation path: /api/platform/v1/banks/current/frontend-config. This read-only route does not require Idempotency-Key; it returns public browser-safe frontend metadata only and never exposes bank secrets, raw MyInfo, credit bureau data, bank statements, raw document contents, NRIC/FIN, income-proof documents, full financial profile data, callback signing secrets, staff write controls, provider calls, or enterprise ingress claims. Live bank frontend config remains unavailable until promotion gates have REST, consent, audit, sandbox, callback, and operations evidence. Bank pilot posture remains information/referral and pre-approval only, recommendation and live bank-decision claims remain deferred, and partner-status publication remains private-first.