Request On Demand Payout

PAY-6 (B-004): customer-initiated on-demand payout request.

For a funded journey whose payout cadence is on_demand, the scheduled generator never auto-opens a cycle (it continues on_demand), so without this endpoint a funded on_demand trader could NEVER withdraw. This opens a cycle covering [last-cycle-end-or-funded-anchor, now], closes it on demand through the SAME _close_cycle_and_create_request path the scheduled generator uses (identical cycle math, eval, equity/min-days/consistency guards, KYC stamp, fee-refund, auto-reject) — no duplicated logic — and returns the resulting payout_request.

Guards:

• journey must be active + on the funded phase + account active;
• cadence must be on_demand (a scheduled-cadence journey 409s — it is served by the generator);
• at most one in-flight payout per account (the partial-unique index plus an explicit pre-check) — a duplicate concurrent request 409s;
• the same min-amount / equity-floating / KYC checks the scheduled path applies (inside _close_cycle_and_create_request) decide payable vs auto-rejected.