feat: replace bind-mount log pipeline with Docker log streaming

Services now print RFC 5424 to stdout; Docker captures via json-file driver.
A new host-side collector (decnet.web.collector) streams docker logs from all
running decky service containers and writes RFC 5424 + parsed JSON to the host
log file. The existing ingester continues to tail the .json file unchanged.
rsyslog can consume the .log file independently — no DECNET involvement needed.

Removes: bind-mount volume injection, _LOG_NETWORK bridge, log_target config
field and --log-target CLI flag, TCP syslog forwarding from service templates.

decnet/web/router/fleet/api_deploy_deckies.py

@@ -50,7 +50,6 @@ async def api_deploy_deckies(req: DeployIniRequest, current_user: str = Depends(
             subnet=subnet_cidr,
             gateway=gateway,
             deckies=[],
-            log_target=ini.log_target,
             log_file=ingest_log_file,
             ipvlan=False,
             mutate_interval=ini.mutate_interval or DEFAULT_MUTATE_INTERVAL