Create the kid account in the input group

Sunshine (running in the kid's session) needs /dev/uinput — group
'input' — to create the virtual mouse/keyboard for Moonlight remote
control; without it the input stream hangs at "establishment" while
video works. Found on hardware; on-box fix is usermod -aG input.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

build-console.sh

@@ -46,6 +46,9 @@ groups = ["wheel"]
 [[customizations.user]]
 name = "$KID_USER"
 password = "$KID_PASSWORD"
+# input: Sunshine needs /dev/uinput (group input) to create the virtual
+# mouse/keyboard for Moonlight remote control
+groups = ["input"]
 EOF
 
 mkdir -p files/console/etc