chore: move loose helper scripts into scripts/, fix doc refs

README.md

@@ -117,6 +117,7 @@ archive/              Retired experiments (predict_new.py, rpo_iki/, simple_pred
                       check/merge/test scripts) — history preserved, not imported
 export_model.py       Export .pt → TensorRT .engine (FP16)  |  export_v4.py  variant
 deploy_to_jetson.py   Paramiko sync + service restart
+scripts/              Loose helpers (frame sampling, DB check, guide PDF)
 *.service             systemd units (counter, dashboard, mediamtx)
 zones.json            Calibrated zone geometry
 batch_history_folder/ Per-batch JSON reports