systemd daemons run with WorkingDirectory=/ by default; docker compose
derives the project name from basename(cwd), which is empty at '/', and
aborts with 'project name must not be empty'. Pass -p decnet explicitly
so the project name is independent of cwd, and set WorkingDirectory=/opt/decnet
on the three DECNET units so compose artifacts (decnet-compose.yml,
build contexts) also land in the install dir.
Rename log-file-path -> log-directory (maps to DECNET_LOG_DIRECTORY). Bundle
now ships three systemd units rendered with agent_name/master_host and installs
them into /etc/systemd/system/. Bootstrap replaces direct 'decnet X --daemon'
calls with systemctl enable --now. Each unit pins DECNET_SYSTEM_LOGS so agent,
forwarder, and deckies logs land at decnet.{agent,forwarder}.log and decnet.log
under /var/log/decnet.
