fix: remove CDROM apt source before package install

Debian netinstall adds cdrom: to sources.list. With the ISO still
attached in the VM, apt-get update fails on it. Strip it before
running apt.

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

install-kiosk.sh

@@ -32,6 +32,7 @@ fi
 
 # ── Packages ───────────────────────────────────────────────────────
 echo "==> Installing packages..."
+sed -i '/^deb cdrom:/d' /etc/apt/sources.list
 apt-get update -qq
 apt-get install -y \
   chromium \