A server that already works as panel + VPN can now also be a node of
another panel without losing its own: `awg-ctrl join` keeps awg-ui running
next to the agent and writes NODE_PANEL=on. `--no-panel` stops it as
before. Both panels talk to the same awg-ctrl, which stays the source of
truth, so they do not get in each other's way.
The CLI runs awg-ctrl, awg-ui and awg-agent on such a node, all behind the
awg-ctrl health gate; a node installed by install.sh has no UI_PASS and
still runs only awg-ctrl + agent. unjoin also drops NODE_PANEL.
maeneko
129f29d6be