fix: use getty auto-login instead of systemd TTY service for first-boot setup

Replaces kiosk-firstboot.service (which got SIGHUP'd by getty) with a
simpler approach: configure getty@tty1 to auto-login root, run kiosk-setup
from .bash_profile. Cleaner TTY ownership — no service/getty conflicts.
install-kiosk.sh now removes the auto-login config and kiosk-setup script
on completion so root doesn't auto-login after the kiosk is running.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

install-kiosk.sh

@@ -146,9 +146,13 @@ chown -R "$KIOSK_USER:$KIOSK_USER" \
   "$HOME_DIR" \
   "$CHROMIUM_PROFILE"
 
-# ── Enable LightDM, remove first-boot service ─────────────────────
+# ── Enable LightDM, remove first-boot setup ───────────────────────
 systemctl enable lightdm
 systemctl set-default graphical.target
+# Remove auto-login and setup script so root doesn't auto-login after kiosk is running
+rm -f /etc/systemd/system/getty@tty1.service.d/autologin.conf
+rm -f /usr/local/bin/kiosk-setup
+# Legacy cleanup (no-op if not present)
 systemctl disable kiosk-firstboot 2>/dev/null || true
 rm -f /etc/systemd/system/kiosk-firstboot.service
 systemctl daemon-reload