fix: VPS xorg-dummy auth + rustdesk-dummy service fixes

- xorg-dummy.service: remove -nolisten local (blocked local UNIX socket)
- xorg-dummy.service: add -auth /root/.Xauthority and xauth generation ExecStartPre
- rustdesk-dummy.service: add XAUTHORITY=/root/.Xauthority env var
- Add config/vps/20-dummy-headless.conf (Xorg dummy config for VPS)
- Disable conflicting gdm.service on VPS
- RustDesk server now starts successfully with DUMMY0 as display

Fixes connection refused on /tmp/.X11-unix/X0 caused by
-nolisten local Xorg flag.

config/vps/20-dummy-headless.conf

@@ -0,0 +1,23 @@
+Section "Device"
+    Identifier "DummyHeadless"
+    Driver "dummy"
+    Option "ConstantDPI" "true"
+    VideoRam 256000
+EndSection
+
+Section "Monitor"
+    Identifier "DummyMonitor"
+    HorizSync 28-80
+    VertRefresh 48-75
+EndSection
+
+Section "Screen"
+    Identifier "DummyScreen"
+    Device "DummyHeadless"
+    Monitor "DummyMonitor"
+    DefaultDepth 24
+    SubSection "Display"
+        Depth 24
+        Modes "1920x1080" "1280x720"
+    EndSubSection
+EndSection

config/vps/rustdesk-dummy.service

@@ -1,5 +1,5 @@
 [Unit]
-Description=RustDesk Server with Dummy Display
+Description=RustDesk with Dummy Display
 After=xorg-dummy.service
 Requires=xorg-dummy.service
 
@@ -7,12 +7,11 @@ Requires=xorg-dummy.service
 Type=simple
 User=root
 Environment="DISPLAY=:0"
-ExecStartPre=/bin/sleep 5
+Environment="XAUTHORITY=/root/.Xauthority"
+ExecStartPre=/bin/sleep 3
 ExecStart=/usr/lib/rustdesk/rustdesk --server
 Restart=always
 RestartSec=10
-StandardOutput=append:/var/log/rdtop-rustdesk.log
-StandardError=append:/var/log/rdtop-rustdesk.log
 
 [Install]
 WantedBy=multi-user.target

config/vps/xorg-dummy.service

@@ -1,25 +1,16 @@
 [Unit]
-Description=Xorg Dummy Display for RustDesk VPS
+Description=Xorg Dummy Display
 After=network.target
 
 [Service]
 Type=simple
 User=root
 Environment="DISPLAY=:0"
+ExecStartPre=/bin/bash -c 'test -f /root/.Xauthority || (xauth -f /root/.Xauthority add :0 . $(mcookie) \u0026\u0026 chmod 600 /root/.Xauthority)'
 ExecStartPre=/bin/mkdir -p /tmp/.X11-unix
-ExecStart=/usr/lib/xorg/Xorg :0 \
-    -nolisten tcp \
-    -nolisten local \
-    -config /etc/X11/xorg.conf.d/99-dummy.conf \
-    +extension GLX \
-    +extension RANDR \
-    +extension RENDER \
-    -novtswitch \
-    -keeptty
+ExecStart=/usr/lib/xorg/Xorg :0     -auth /root/.Xauthority     -nolisten tcp     -config /etc/X11/xorg.conf.d/20-dummy-headless.conf     +extension GLX     +extension RANDR     +extension RENDER     -novtswitch     -keeptty
 Restart=always
 RestartSec=5
-StandardOutput=append:/var/log/rdtop-xorg.log
-StandardError=append:/var/log/rdtop-xorg.log
 
 [Install]
 WantedBy=multi-user.target