nextwks.sh: add root check with clear error message

tools/nextwks.sh

@@ -21,6 +21,13 @@ usage() {
 MODE="${1#--}"
 case "$MODE" in install|update|destroy) ;; *) usage ;; esac
 
+# --- Must be root ---
+if [ "$(id -u)" -ne 0 ]; then
+    echo "ERROR: This script must be run as root (use sudo)."
+    echo "  sudo bash ~/nextwks.sh --$MODE"
+    exit 1
+fi
+
 # --- Load existing env (if any) ---
 if [ -f "$BACKUP_DIR/.env" ]; then
     set -a; source "$BACKUP_DIR/.env"; set +a