feat: working XFCE + RustDesk online on VPS tmux

- Add start-rd-desktop.sh: Xvfb :99 + xfwm4 + xfce4-panel + RustDesk client
- Add rustdesk-vps.service (Type=simple, but systemd kills processes) → use tmux instead
- Update README.md with VPS architecture (Xvfb + xfce4-session + RustDesk)
- Update VPS section: tmux persistent session instead of systemd
- RustDesk ID: 458564614, password: retrowest
- Ports 21115-21119 open in UFW for Docker server (optional)
- XFCE desktop confirmed working (xfdesktop + xfwm4 + panel)

Note: systemd ExecStartPre kills background processes (Xvfb, xfce4).
Solution: tmux detached session 'rd' with start-rd-desktop.sh

config/vps/rustdesk-vps.service

@@ -1,17 +1,19 @@
 [Unit]
-Description=RustDesk VPS Client
-After=network.target
+Description=RustDesk + XFCE Desktop on VPS
+After=network-online.target
 
 [Service]
-Type=simple
+Type=forking
 User=root
 Environment="DISPLAY=:99"
-ExecStartPre=-/usr/bin/pkill -9 Xvfb
-ExecStart=/usr/local/bin/rustdesk-vps-start.sh
+Environment="XAUTHORITY=/root/.Xauthority"
+
+# Start Xvfb, wait for display, then launch XFCE + RustDesk
+ExecStartPre=/bin/bash -c 'pkill -9 -f rustdesk 2>/dev/null || true; pkill -9 -f xfce4-session 2>/dev/null || true; sleep 1; pkill -9 Xvfb 2>/dev/null || true; rm -f /tmp/.X11-unix/X99; sleep 1'
+ExecStart=/bin/bash -c 'Xvfb :99 -screen 0 1920x1080x24 -ac +extension RANDR > /dev/null 2>&1 &; sleep 3; for i in $(seq 1 30); do export DISPLAY=:99; export XAUTHORITY=/root/.Xauthority; xrandr --listmonitors > /dev/null 2>&1 && break; sleep 1; done; nohup dbus-run-session -- xfce4-session > /tmp/xfce-session.log 2>&1 &; sleep 5; nohup dbus-run-session -- /usr/share/rustdesk/rustdesk --server > /tmp/rustdesk-session.log 2>&1 &; sleep 2; exit 0'
+ExecStop=/bin/bash -c 'pkill -9 -f rustdesk; pkill -9 -f xfce4-session; pkill -9 Xvfb; rm -rf /tmp/RustDesk'
 Restart=always
-RestartSec=5
-StandardOutput=journal
-StandardError=journal
+RestartSec=10
 
 [Install]
 WantedBy=multi-user.target