K-114: SSH root login prompt with sshd drop-in in the install path

prompt_lxc_config asks 'SSH-Root-Login erlauben? [Y/n]' (env-presettable
via SSH_ROOT_LOGIN, validated, normalized to yes|no). The bootstrap passes
the value into the container; configure_ssh_root_login writes
/etc/ssh/sshd_config.d/zz-root-login.conf (yes -> PermitRootLogin yes,
no -> prohibit-password) and reloads sshd.

lib/install.func

@@ -38,6 +38,36 @@ apt_cleanup() {
   apt-get autoclean -qq >/dev/null || true
 }
 
+# ── ssh ──────────────────────────────────────────────────────────────────────
+# SSH-Root-Login gemäß Host-Prompt (prompt_lxc_config setzt SSH_ROOT_LOGIN,
+# bootstrap_install_script reicht es als Env durch; Default: yes).
+#   yes → PermitRootLogin yes (Passwort-Login mit dem generierten Root-Passwort)
+#   no  → PermitRootLogin prohibit-password (Debian-Default, nur SSH-Key)
+# Umsetzung als Drop-in, damit Paket-Updates von sshd_config nicht kollidieren.
+configure_ssh_root_login() {
+  local choice="${SSH_ROOT_LOGIN:-yes}" value
+  case "$choice" in
+    yes) value="yes" ;;
+    no)  value="prohibit-password" ;;
+    *)   msg_err "SSH_ROOT_LOGIN must be yes|no, got: '$choice'"; return 1 ;;
+  esac
+
+  if [[ ! -d /etc/ssh/sshd_config.d ]]; then
+    if [[ "$choice" == "no" ]]; then
+      msg_warn "openssh-server not installed — nothing to configure (root login stays off)"
+      return 0
+    fi
+    msg_info "Installing openssh-server..."
+    apt-get install -y -qq openssh-server >/dev/null
+  fi
+
+  msg_info "Configuring SSH root login: PermitRootLogin $value"
+  printf 'PermitRootLogin %s\n' "$value" >/etc/ssh/sshd_config.d/zz-root-login.conf
+  systemctl reload ssh 2>/dev/null || systemctl restart ssh 2>/dev/null \
+    || msg_warn "ssh.service not active yet — config applies on first start"
+  msg_ok "SSH root login: $choice"
+}
+
 # ── users / dirs ─────────────────────────────────────────────────────────────
 create_system_user() {
   local user="$1" home="$2"