fix(deploy): relocate StandardOutput/StandardError below multi-line ExecStart

Four templates use backslash line-continuation on ExecStart
(decnet-bus, decnet-forwarder, decnet-listener, decnet-updater). My
earlier sed inserted StandardOutput= and StandardError= right after
the first ExecStart= line, which split the command and systemd fed
those two lines back to the binary as extra positional arguments —
the bus in particular crashed with:

  Got unexpected extra argument
  (StandardOutput=append:/var/log/decnet/decnet.bus.log)

Walk the ExecStart block (follow \-continuation lines) and insert
the two Standard* directives AFTER the last continuation line. The
nine single-line ExecStart templates are unaffected in shape but
re-written through the same path to keep the whole set uniform.

deploy/decnet-bus.service.j2

@@ -18,10 +18,10 @@ RuntimeDirectory=decnet
 RuntimeDirectoryMode=0755
 Environment=DECNET_SYSTEM_LOGS=/var/log/decnet/decnet.bus.log
 ExecStart={{ venv_dir }}/bin/decnet bus \
-StandardOutput=append:/var/log/decnet/decnet.bus.log
-StandardError=append:/var/log/decnet/decnet.bus.log
     --socket /run/decnet/bus.sock \
     --group decnet
+StandardOutput=append:/var/log/decnet/decnet.bus.log
+StandardError=append:/var/log/decnet/decnet.bus.log
 
 # No privileged network operations — UNIX-domain socket only.
 CapabilityBoundingSet=