Creates a Ticket Timer that starts running

Required permission: Ticket Timers - Overview

Creates a Ticket Timer that starts directly in status_running (start_time is set to now, end_time is left unset). The timer always belongs to the authenticated technician — any client-supplied user_id is ignored.

A technician holds at most one active timer per ticket. If they already have a running or paused timer on the ticket it is resumed and returned with a 200 rather than a second timer being created, and the request body is ignored.

An omitted or null billable resolves to the account's "time is non-billable by default" setting, matching the Web App.