Harden operator YOLO training runtime

backend/README.md

@@ -283,7 +283,7 @@ candidates are too weak for the target imagery. It is not a browser feature and
 does not change API contracts:
 
 ```bash
-docker exec -it geointel python /app/scripts/export_operator_yolo_dataset.py \
+docker exec -it geointel python3 /app/scripts/export_operator_yolo_dataset.py \
   --manifest-path /app/storage/operator-data/operator_samples_manifest.json \
   --output-dir /app/storage/operator-data/yolo-building-dataset \
   --val-samples turnhout \
@@ -302,6 +302,7 @@ docker exec \
   -e TRAIN_BATCH=2 \
   -e TRAIN_WORKERS=0 \
   -e TRAIN_DEVICE=cpu \
+  -e PYTHON_BIN=python3 \
   geointel bash /app/scripts/train_operator_yolo_detector.sh
 ```