Add host maintenance mode and NUT/Tailscale helpers

prox-maintenance-mode.sh saves and clears onboot/startup across all VMs and
CTs so a host can be rebooted without guests coming back up, then restores
the saved state. Supports --status and --dry-run.

nut-udev-restart.sh restarts the NUT UPS driver on a USB re-enumeration
event. tailscale-optimize-router.sh applies the recommended UDP GRO
forwarding offloads for subnet routers.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

nut-udev-restart.sh

@@ -0,0 +1,14 @@
+#!/bin/bash
+# nut-udev-restart.sh - safely restart NUT UPS driver on USB event
+# Location: /opt/ergosteur/nut-udev-restart.sh
+
+(
+    # small delay so the USB device is fully settled before restarting driver
+    sleep 2
+
+    # stop and start the driver
+    /sbin/upsdrvctl stop
+    /sbin/upsdrvctl start
+) &
+
+exit 0