fix(console): the dashboard can redraw over the shutdown message during a long teardown #370

What happened

Since #366 the node shows a branded message when it reboots or powers off. During a long orderly teardown (services stopping, the state volume closing), the console dashboard process is still running and keeps redrawing its status screen on its normal refresh. A redraw can land after the shutdown message is written and paint over it, so the operator sees the ordinary status screen (or a mix of both) instead of the shutdown message until the screen goes dark.

Expected behavior

Once a reboot or power-off starts, the dashboard stops drawing for good (it is told to stop, or stopped, before the shutdown message is written), and the shutdown message stays on screen until the machine resets or powers off. A test covers the order: no dashboard frame after the shutdown message.

Environment

cryptos-node main after #366 (internal/init teardown order, cmd/cryptos-console refresh loop, internal/console shutdown screen). Seen in review of the #363 fix; not yet reproduced on lab hardware.