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-updater.service.j2

@@ -14,12 +14,12 @@ WorkingDirectory={{ install_dir }}
 EnvironmentFile=-{{ install_dir }}/.env.local
 Environment=DECNET_SYSTEM_LOGS=/var/log/decnet/decnet.updater.log
 ExecStart={{ venv_dir }}/bin/decnet updater \
-StandardOutput=append:/var/log/decnet/decnet.updater.log
-StandardError=append:/var/log/decnet/decnet.updater.log
     --host 0.0.0.0 --port 8766 \
     --updater-dir /etc/decnet/updater \
     --install-dir {{ install_dir }} \
     --agent-dir /etc/decnet/agent
+StandardOutput=append:/var/log/decnet/decnet.updater.log
+StandardError=append:/var/log/decnet/decnet.updater.log
 
 # The updater SIGTERMs the agent and spawns a new one. Same User=decnet means
 # signalling is allowed without CAP_KILL. It does not need NET_ADMIN/NET_RAW