Stage 1 base config/hardening toolset, applied and verified on pve1

Splits the repo into Stage 1 (base host config/hardening, applies to any
node) and Stage 2 (future HA/Ceph cluster, deferred - pve1's mini-PC
hardware can't support the assumed split-disk/multi-NIC layout).

Adds the Stage 1 toolset: firewall deploy, named admin user creation,
unattended security upgrades, subscription-nag removal (with an apt hook
so the patch survives package updates), and a read-only audit script.
Fixes switch-to-no-subscription-repo.sh, which only handled the legacy
.list format and silently no-op'd against PVE 9's deb822 .sources files;
it now removes enterprise sources outright rather than commenting them
out. Shared logic (root check, idempotent file writes, backups) factored
into scripts/lib/common.sh.

Ran the full sequence against pve1 via scripts/bootstrap.sh +
create-admin-user.sh; scripts/audit.sh confirms all checks pass.

scripts/lib/nag-patch.sh

@@ -0,0 +1,22 @@
+#!/bin/bash
+# Neutralizes the Proxmox "No valid subscription" nag (login popup and the
+# dashboard subscription indicator) by patching proxmox-widget-toolkit's
+# proxmoxlib.js. Cosmetic only - doesn't create or spoof a subscription
+# anywhere except this UI check.
+#
+# This file is not run from the repo directly - disable-subscription-nag.sh
+# installs a copy of it to /usr/local/sbin and wires it into an apt
+# Post-Invoke hook, because a proxmox-widget-toolkit package upgrade
+# overwrites proxmoxlib.js and reverts the patch. Idempotent: exits quietly
+# if already patched or if the file isn't present.
+set -euo pipefail
+
+JS_FILE="/usr/share/javascript/proxmox-widget-toolkit/proxmoxlib.js"
+[ -f "$JS_FILE" ] || exit 0
+
+PATTERN="data.status.toLowerCase() !== 'active'"
+grep -qF "$PATTERN" "$JS_FILE" || exit 0
+
+cp "$JS_FILE" "${JS_FILE}.bak.$(date +%s)"
+sed -i "s/${PATTERN}/false/g" "$JS_FILE"
+echo "Patched subscription nag in $JS_FILE"