fix: bound detection QA to inference coverage

backend/app/services/qa_service.py

@@ -8,6 +8,7 @@ from uuid import UUID
 from geoalchemy2.shape import to_shape
 from shapely.geometry import GeometryCollection
 from shapely.geometry.base import BaseGeometry
+from shapely.strtree import STRtree
 from shapely.ops import unary_union
 from shapely.validation import make_valid
 from shapely.geometry import shape
@@ -160,7 +161,10 @@ class QaService:
                 ],
             )
 
-        unmatched_reference_indices = set(range(len(reference_supported)))
+        reference_tree = STRtree([geometry for _, _, geometry in reference_supported])
+        unmatched_reference_indices = {
+            index for index, (_, _, geometry) in enumerate(reference_supported) if geometry.area > 0
+        }
         evidence = QaMatchEvidence(warnings=[f"Unsupported geometry types: {unsupported}"] if unsupported else [], unsupported=bool(unsupported))
 
         for source_index, source_feature, source_geom in source_supported:
@@ -172,11 +176,11 @@ class QaService:
 
             best_iou = 0.0
             best_index = None
-            for reference_index in list(unmatched_reference_indices):
-                _, _, reference_geom = reference_supported[reference_index]
-                if reference_geom.area <= 0:
-                    unmatched_reference_indices.discard(reference_index)
+            candidate_reference_indices = sorted(int(index) for index in reference_tree.query(source_geom))
+            for reference_index in candidate_reference_indices:
+                if reference_index not in unmatched_reference_indices:
                     continue
+                _, _, reference_geom = reference_supported[reference_index]
                 try:
                     intersection = source_geom.intersection(reference_geom)
                 except Exception as exc:  # pragma: no cover - robustness path