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/conpot/entrypoint.py

@@ -3,7 +3,7 @@
 Entrypoint wrapper for the Conpot ICS/SCADA honeypot.
 
 Launches conpot as a child process and bridges its log output into the
-DECNET structured syslog pipeline.  Each line from conpot stdout/stderr
+syslog-relay structured syslog pipeline.  Each line from conpot stdout/stderr
 is classified and emitted as an RFC 5424 syslog line so the host-side
 collector can ingest it alongside every other service.
 
@@ -21,7 +21,7 @@ from datetime import datetime, timezone
 # ── RFC 5424 inline formatter (Python 3.6-compatible) ─────────────────────────
 
 _FACILITY_LOCAL0 = 16
-_SD_ID = "decnet@55555"
+_SD_ID = "relay@55555"
 _NILVALUE = "-"
 
 SEVERITY_INFO    = 6