feat: Project Scaffold and Docker Packaging

crontab/install-cron.sh

@@ -0,0 +1,23 @@
+#!/bin/bash
+set -euo pipefail
+
+CRON_FILE="${1:-/etc/cron.d/tenbackward}"
+
+if [ ! -f "${CRON_FILE}" ]; then
+    echo "install-cron: cron file ${CRON_FILE} does not exist" >&2
+    exit 1
+fi
+
+if grep -q '__RUN_AT__' "${CRON_FILE}"; then
+    echo "install-cron: refusing to install cron file with unresolved __RUN_AT__ placeholder" >&2
+    exit 1
+fi
+
+chmod 0644 "${CRON_FILE}"
+
+if ! head -n 1 "${CRON_FILE}" | grep -qE '^[A-Z_]+='; then
+    echo "install-cron: ${CRON_FILE} must start with a cron env line (e.g. SHELL=/bin/bash)" >&2
+    exit 1
+fi
+
+echo "install-cron: ${CRON_FILE} installed (mode 0644)"