refactor: strip DECNET tokens from container-visible surface

Rename the container-side logging module decnet_logging → syslog_bridge
(canonical at templates/syslog_bridge.py, synced into each template by
the deployer). Drop the stale per-template copies; setuptools find was
picking them up anyway. Swap useradd/USER/chown "decnet" for "logrelay"
so no obvious token appears in the rendered container image.

Apply the same cloaking pattern to the telnet template that SSH got:
syslog pipe moves to /run/systemd/journal/syslog-relay and the relay
is cat'd via exec -a "systemd-journal-fwd". rsyslog.d conf rename
99-decnet.conf → 50-journal-forward.conf. SSH capture script:
/var/decnet/captured → /var/lib/systemd/coredump (real systemd path),
logger tag decnet-capture → systemd-journal. Compose volume updated
to match the new in-container quarantine path.

SD element ID shifts decnet@55555 → relay@55555; synced across
collector, parser, sniffer, prober, formatter, tests, and docs so the
host-side pipeline still matches what containers emit.

templates/cowrie/Dockerfile

@@ -7,7 +7,7 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     git authbind \
     && rm -rf /var/lib/apt/lists/*
 
-RUN useradd -r -s /bin/false -d /opt decnet \
+RUN useradd -r -s /bin/false -d /opt logrelay \
  && apt-get update && apt-get install -y --no-install-recommends libcap2-bin \
  && rm -rf /var/lib/apt/lists/* \
  && (find /usr/bin/ -maxdepth 1 -name 'python3*' -type f -exec setcap 'cap_net_bind_service+eip' {} \; 2>/dev/null || true)
@@ -18,5 +18,5 @@ RUN chmod +x /entrypoint.sh
 HEALTHCHECK --interval=30s --timeout=5s --start-period=10s --retries=3 \
   CMD kill -0 1 || exit 1
 
-USER decnet
+USER logrelay
 ENTRYPOINT ["/entrypoint.sh"]