Add encoding.lp (0 = auto) so a long encode can be capped to N logical
processors instead of pinning every core, as a lighter-weight alternative to
the compose cgroup limit. Threaded config -> types.Job -> -svtav1-params via a
testable svtav1Params helper. Settings-UI surfacing stays with #1.
refs #5
EXPOSE 8080 in the image, publish 8080 in compose, document http_addr in the
example config, and add the CPU/memory limits so a long encode can't starve
the host.