Add MTU migration rollback script

scripts/network/mtu_rollback.sh

@@ -0,0 +1,20 @@
+#!/bin/bash
+# ROLLBACK — restore daemon.json to original (no mtu field)
+HOST=$(hostname)
+LOG=/volume1/docker/mtu_migration/${HOST}_rollback.log
+exec >> "$LOG" 2>&1
+echo "[$(date)] $HOST ROLLBACK starting"
+cat > /etc/docker/daemon.json << 'DAEMON'
+{
+  "data-root": "/volume1/docker-root/",
+  "storage-driver": "overlay2",
+  "dns-search": ["."]
+}
+DAEMON
+echo "[$(date)] daemon.json restored: $(cat /etc/docker/daemon.json)"
+systemctl restart docker
+sleep 15
+echo "[$(date)] Docker status: $(systemctl is-active docker)"
+echo "[$(date)] eth0 MTU: $(ip link show eth0 | grep -o 'mtu [0-9]*')"
+touch /volume1/docker/mtu_migration/${HOST}_rollback.done
+echo "[$(date)] $HOST ROLLBACK COMPLETE"