Add a WiFi screen to the kiosk app (Shift+W+S+F+H)

With the virtual consoles turned off there was no way to join a WiFi
network at the kiosk itself. Holding Shift+W+S+F+H together (or
Ctrl+Alt+Shift+Super+W) now opens a PIN-protected WiFi screen: scan,
pick or type a network, enter the password, connect.

The root side is a small helper (kiosk-wifi-helper: status, scan,
connect only) that the kiosk user may run through a validated
sudoers.d rule. It writes the same netplan file as Core Settings ->
WiFi and puts the previous one back if the new network gives no
address. Installed by provisioning and Advanced -> Upgrade, removed by
Complete Uninstall.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Cjz8a58eB5P9sUweqd3NHm

menus/complete_uninstall.sh

@@ -116,6 +116,7 @@ action_complete_uninstall() {
 
     echo "[7/12] Removing remaining scripts..."
     sudo rm -f "$BIN_DIR"/kiosk-*
+    sudo rm -f "$SUDOERS_D_DIR/kiosk-wifi"
     sudo rm -f /etc/udev/rules.d/99-kiosk-hotplug.rules
     sudo udevadm control --reload-rules 2>/dev/null || true