Fix a brief audio hiccup on the first playback after starting the server (#5577)

The first Sendspin stream of a server run loaded its audio library on the event loop, freezing audio production for up to half a second and leaving a hole in the play timeline. Loading it up front, off the loop, removes the hiccup.

Also fixes the slow-SQL debug warning, which timed how long the server waited for a query rather than how long the query took, so any unrelated freeze was reported as a slow query.