Add firewall (nftables, iptables)

[jeremy-code]

Add firewall (nftables, iptables) to block traffic coming out except for the following:

1. Ubuntu
2. Cloudflare (https://developers.cloudflare.com/cloudflare-one/networks/connectors/cloudflare-tunnel/configure-tunnels/tunnel-with-firewall/#required-for-tunnel-operation)
3. foldingathome (https://docs.foldingathome.org/ws/install.html#network-requirements)
4. Oracle Cloud
5. The domains Vaultwarden needs

...etc