Add dockhand role to initial_install

Tagged never,dockhand_install so it only runs when explicitly requested.
Installs docker.io + docker-compose-v2, templates a compose file for
fnsys/dockhand:latest at /docker/dockhand, and wires a oneshot systemd
unit that brings the stack up.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

initial_install/roles/dockhand/templates/dockhand.service.j2

@@ -0,0 +1,16 @@
+[Unit]
+Description=dockhand (docker compose stack)
+Requires=docker.service
+After=docker.service network-online.target
+Wants=network-online.target
+
+[Service]
+Type=oneshot
+RemainAfterExit=yes
+WorkingDirectory=/docker/dockhand
+ExecStart=/usr/bin/docker compose up -d --remove-orphans
+ExecStop=/usr/bin/docker compose down
+TimeoutStartSec=300
+
+[Install]
+WantedBy=multi-user.target