refactor: prefer systemd sockets over socat

- Document preferred method for socket use depending on use case;
- Fix Github web-flow key;
- Standardize naming of services;
- Use sys-ssh in ansible formula;
- Start services conditionally with Qubes Service and evaluated by
  systemd ConditionPathExists= instead of installing on a per qube basis
  with rc.local scripts;
- Change Qusal services to "qusal-" prefix instead of "qubes-" prefix.

Fixes: https://github.com/ben-grande/qusal/issues/80
Fixes: https://github.com/ben-grande/qusal/issues/79

salt/sys-ssh-agent/files/client/systemd/qubes-ssh-agent-forwarder@.service

@@ -1,18 +0,0 @@
-# SPDX-FileCopyrightText: 2023 Benjamin Grande M. S. <ben.grande.b@gmail.com>
-#
-# SPDX-License-Identifier: AGPL-3.0-or-later
-
-[Unit]
-Description=SSH Agent Forwarder to Qrexec SSH Agent %i
-
-[Service]
-User=user
-Group=user
-Type=simple
-UMask=0177
-ExecStartPre=/usr/bin/mkdir -m 700 -p %T/%p
-ExecStartPre=/usr/bin/ssh-agent -a %T/%p/%i.sock
-ExecStart=/usr/bin/socat UNIX-LISTEN:"%T/%p/%i.sock,unlink-early,reuseaddr,fork" EXEC:"qrexec-client-vm -- @default qusal.SshAgent+%i"
-
-[Install]
-WantedBy=default.target