Add manual world backup script

Flushes world via rcon (save-off + save-all flush) before tarring
when the server is running; skips the flush and archives as-is when
the container is down. Outputs timestamped archives to backups/,
which is gitignored.

backup.sh

@@ -0,0 +1,29 @@
+#!/usr/bin/env bash
+# Usage: ./backup.sh [label]
+# Creates backups/world-YYYY-MM-DD-HHMM[-label].tar.gz
+# If the minecraft container is running, flushes world via rcon first.
+set -euo pipefail
+
+cd "$(dirname "$0")"
+
+LABEL="${1:-}"
+STAMP="$(date +%Y-%m-%d-%H%M)"
+SUFFIX="${LABEL:+-$LABEL}"
+OUT="backups/world-${STAMP}${SUFFIX}.tar.gz"
+
+mkdir -p backups
+
+if docker ps --format '{{.Names}}' | grep -qx minecraft; then
+    echo "Server running — flushing world via rcon..."
+    docker exec minecraft rcon-cli save-off >/dev/null
+    docker exec minecraft rcon-cli save-all flush >/dev/null
+    trap 'docker exec minecraft rcon-cli save-on >/dev/null || true' EXIT
+else
+    echo "Server not running — archiving world as-is."
+fi
+
+echo "Archiving data/world -> ${OUT}"
+tar -czf "${OUT}" -C data world
+
+echo "Done."
+ls -lh "${OUT}"