Run an audit now.

Makes the audit’s queue row due immediately; the dispatcher claims it on its next tick, so the 202 means “queued”, not “finished” — poll GET /audits/{id}/runs for the result. Three cases all answer 409 and are distinguished by the error field: the audit is unknown or belongs to another organization, it is disabled (a disabled audit has no queue row), or a run is already in progress, which must finish before another can be queued.