Start system DBus inside container session.

Launch dbus-daemon before Xorg so libinput/seat integration has a system bus, reducing input routing issues in headless Sunshine sessions.

Co-authored-by: Cursor <cursoragent@cursor.com>

Dockerfile

@@ -92,6 +92,8 @@ mkdir -p /home/steam/.local/share/Steam /tmp/xdg-steam\n\
 ln -sfn /home/steam/.local/share/Steam /home/steam/.steam\n\
 chown -R steam:steam /home/steam /tmp/xdg-steam\n\
 modprobe uinput >/dev/null 2>&1 || true\n\
+mkdir -p /run/dbus\n\
+dbus-daemon --system --fork || true\n\
 Xorg :99 -config /etc/X11/xorg-dummy.conf -nolisten tcp -noreset +extension GLX +extension RANDR +extension RENDER &\n\
 export DISPLAY=:99\n\
 export HOME=/root\n\