restrict postcode distance computation to within country

src/nominatim_api/search/db_searches/address_search.py

@@ -233,6 +233,7 @@ class AddressSearch(base.AbstractSearch):
             pc_near = sa.select(sa.func.min(tpc.c.geometry.ST_Distance(t.c.centroid)
                                             * (tpc.c.rank_search - 19)))\
                         .where(tpc.c.postcode.in_(pcs))\
+                        .where(tpc.c.country_code == t.c.country_code)\
                         .scalar_subquery()
             penalty += sa.case((t.c.postcode.in_(pcs), 0.0),
                                else_=sa.func.coalesce(pc_near, cast(SaColumn, 2.0)))