Add NetBird update scripts and README

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

update-netbird-server.sh

@@ -0,0 +1,36 @@
+#!/usr/bin/env bash
+# Update the self-hosted NetBird server stack (Docker Compose).
+# Backs up config files and the netbird_data volume before upgrading.
+set -euo pipefail
+
+STACK_DIR=/var/limonia/netbird
+DATA_VOLUME=netbird_netbird_data
+BACKUP_DIR="$HOME/netbird-backups/$(date +%F_%H%M%S)"
+
+cd "$STACK_DIR"
+mkdir -p "$BACKUP_DIR"
+
+echo "Current images:"
+docker compose images
+
+# Pull first so downtime is only the backup + restart
+docker compose pull
+
+echo "Backing up config to $BACKUP_DIR"
+tar czf "$BACKUP_DIR/config.tgz" -C "$STACK_DIR" .
+
+# Stop the server so the data store is copied consistently
+docker compose stop netbird-server
+echo "Backing up volume $DATA_VOLUME"
+docker run --rm -v "$DATA_VOLUME":/data:ro -v "$BACKUP_DIR":/backup alpine \
+  tar czf /backup/netbird_data.tgz -C /data .
+
+docker compose up -d
+sleep 5
+
+echo "Updated images:"
+docker compose images
+docker compose ps
+docker compose logs --tail 30 netbird-server
+
+echo "Backup saved in $BACKUP_DIR"