Adds a gnss-simulator service to docker-compose.yaml, sharing
maptool's network namespace (network_mode: "service:maptool") so it's
reachable at the 127.0.0.1:2947 GpsdClient hardcodes -- there's no
real receiver attached to the server, so without this the "GNSS"
control there always shows "no fix". Both services now reference the
same image (maptool:latest) explicitly rather than each service with
its own `build: .` producing two separately-tagged (if
identically-layered) images.
Verified for real: built and ran the full compose stack in an
isolated project/port on cube (not the live one), confirmed
/api/gnss/position reports a moving fix across two polls through the
actual sidecar networking, then tore it down completely -- containers,
image, network, temp checkout. Production's own stack was untouched
throughout and confirmed still healthy afterward.
randy
3e81ee8015