24x7 RTMP desktop stream, client side + UAT PASS (#798)

Whole-screen KDE capture -> x264 -> RTMP, fenced to the rt slice.
Loopback mediamtx receiver; Cloudron cutover = one creds edit.
Detail: https://projects.knownelement.com/issues/798#note-4519

💘 Generated with Crush

Assisted-by: Crush:glm-5.2

staged/systemd/ukrrs-rtmp-stream.service

@@ -0,0 +1,24 @@
+[Unit]
+Description=UKRRS 24x7 desktop RTMP stream (reachableceo KDE whole screen)
+Documentation=file:///home/reachableceo/projects/ultix/STREAMING.md
+After=network-online.target xrdp.service
+Wants=network-online.target
+
+[Service]
+Type=simple
+User=reachableceo
+Group=reachableceo
+Slice=ukrrs-rt.slice
+Environment=HOME=/home/reachableceo
+Environment=XDG_RUNTIME_DIR=/run/user/1001
+EnvironmentFile=/etc/ukrrs/rtmp-stream.env
+ExecStart=/usr/local/sbin/ukrrs-rtmp-stream.sh
+Restart=always
+RestartSec=5
+StartLimitIntervalSec=0
+# hard stop of the wrapper must take ffmpeg with it
+KillMode=control-group
+TimeoutStopSec=15
+
+[Install]
+WantedBy=multi-user.target