Close every open position on one account at market.

This is irreversible. Use with caution. Pending orders are untouched — cancel those with POST /v1/orders/cancel-all.

Request Body:

{ "account_number": "11111115" }

Replaces: POST /api/v1/accounts/{account_number}/close-trades and POST /api/v1/crm/users/{login_id}/close-trades. Note the old endpoints also cancelled pending orders; this one does not.