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.

development/docs/services/COLLECTOR.md

@@ -31,7 +31,7 @@ The main asynchronous entry point.
 
 DECNET services emit logs using a standardized RFC 5424 format with structured data. The `parse_rfc5424` function is the primary tool for extracting this information.
 
-- **Structured Data**: Extracts parameters from the `decnet@55555` SD-ELEMENT.
+- **Structured Data**: Extracts parameters from the `relay@55555` SD-ELEMENT.
 - **Field Mapping**: Identifies the `attacker_ip` by scanning common source IP fields (`src_ip`, `client_ip`, etc.).
 - **Consistency**: Formats timestamps into a human-readable `%Y-%m-%d %H:%M:%S` format for the analytical stream.