Raise configured YOLO max detections

backend/README.md

@@ -359,6 +359,7 @@ YOLO_CONFIG_DIR=/app/storage/ultralytics
 YOLO_DEVICE=cpu
 YOLO_IMAGE_SIZE=640
 YOLO_MAX_TILES=100
+YOLO_MAX_DETECTIONS=1000
 YOLO_BATCH_SIZE=1
 ```
 
@@ -384,6 +385,10 @@ python scripts/yolo_preflight.py --model-path /absolute/path/to/local-model.pt -
 
 The preflight checks configuration, dependency availability, local model file existence, tile manifest validity, tile count and referenced tile paths. JSON output also includes runtime diagnostics for the model directory, `YOLO_CONFIG_DIR`, installed `torch`/`ultralytics` versions and CUDA availability when dependency checks pass. It does not load a YOLO model, run inference or download weights.
 
+`YOLO_MAX_DETECTIONS` is forwarded to Ultralytics as `max_det`. The default is
+`1000` because dense building AOIs can exceed the upstream default cap of 300
+detections before QA/QC can measure recall honestly.
+
 The same read-only status is available through the API and Detection Lab UI:
 
 ```bash