Add lock files and cron setup

run-import.sh

@@ -1,6 +1,17 @@
 #!/usr/bin/env bash
 set -e
 
+# Prevent multiple simultaneous runs by using a lock file specific to this
+# script. If the lock already exists, assume another instance is running and
+# exit gracefully.
+LOCK_FILE="/tmp/$(basename "$0").lock"
+if [ -e "$LOCK_FILE" ]; then
+    echo "[WARN] $(basename "$0") is already running (lock file present)." >&2
+    exit 0
+fi
+touch "$LOCK_FILE"
+trap 'rm -f "$LOCK_FILE"' EXIT
+
 # Ensure virtual environment exists
 if [ ! -d ".venv" ]; then
     echo "[INFO] Creating virtual environment..."