Replace ST_Intersects(district.geom, quarter.geom) with ST_Within(ST_Centroid(quarter.geom), district.geom)
so each cadastral quarter is assigned to exactly one district. Eliminates 85 double-counted quarter-district
pairs and 307 spurious deal-district rows that were skewing PERCENTILE_CONT medians. Function signature
unchanged; no backend code changes required.
