docs: re-shoot nodes-graph + nodes-table with realistic latency + traffic

The previous re-shot pair was missing the demo-cluster's netem injection
and traffic generator, so they showed near-zero latency labels and
empty stat cards. Per docs/demo-screenshot-setup.md the demo intends:

* netem one-way delay per peer (sg=2ms ... br=165ms) so RTT labels show
  believable cross-region values (here: 23–266 ms range)
* live SOCKS5 traffic from demo-hub through alice/bob/... users to peer
  HTTP servers, populating Total Traffic, Realtime Speed sparkline, and
  Connections; sg/sg-r1/sg-r1-a dial HUB inbound to set Exit Clients=3

Re-applied netem to all running demo peers, ran the bundled traffic-gen
script, and reshot the two stat cards now visible: max 16 MB/s peak on
the realtime sparkline, 1.5 GB cumulative download, 10 active streams.

Demo containers are now stopped to leave the workstation idle; restart
with `docker compose -f test/docker-compose.demo.yml start` (data volumes
preserved).

Author: FrankoonG