feat(scripts): add update_crontab.sh for post-migration crontab fix

Idempotent sed-based rewrite of any crontab line that references
/home/moltbot/clawd/tools/backup_config.sh so it points at the
echo-core copy. Safe to re-run; prints a single status line either way.

scripts/update_crontab.sh

@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+# update_crontab.sh — post-migration crontab update for Marius.
+# Replaces the clawd/tools/backup_config.sh line with the echo-core equivalent.
+# Idempotent: safe to re-run.
+set -euo pipefail
+current=$(crontab -l 2>/dev/null || true)
+new=$(printf '%s\n' "$current" | sed -E 's#/home/moltbot/clawd/tools/backup_config\.sh#/home/moltbot/echo-core/tools/backup_config.sh#g')
+if [ "$current" != "$new" ]; then
+  printf '%s\n' "$new" | crontab -
+  echo "Crontab updated: backup_config.sh path remapped to echo-core."
+else
+  echo "Crontab unchanged (already pointing at echo-core, or backup_config line absent)."
+fi