[borodino] refactor(wg-gateway): migrate from Swarm service to standalone privileged container

Commit `8e6cd29`

Remove wg-gateway from borodino Swarm stack (incl. protonvpn secrets)
Deploy as standalone docker-compose on meta-68 with privileged:true → fixes iptables FORWARD (was 0 pkts with only cap_add NET_ADMIN)
scan_net routing confirmed: ak47/bm12 exit via ProtonVPN (103.125.235.24)
Config: /home/docker/wg-gateway/docker-compose.yml on meta-68

Co-Authored-By: Claude Sonnet 4.6 noreply@anthropic.com