make server starts a Go binary that serves both /api/v1/... and the
built frontend on a single port.
A user can open the app on a phone and on a desktop browser at the same
time, control the same locomotive, and observe each other's changes
in real time.
An external throttle changing the speed of a subscribed locomotive on
the command station is reflected in the UI within a single polling
interval.
Killing and restarting the Go binary causes the frontend to reconnect
automatically and resubscribe to the previously controlled locomotives
without a manual page reload.