The "Сети" section table summarised engineering networks and distances, but
users could not see those points on the map. Three root causes:
- Connection-points layer was always empty: NSPD engineering_structures
(cat 36328) arrive as Polygon/MultiPolygon in EPSG:3857 (prod: 587 Polygon
+ 298 MultiPolygon, zero Point), but extractLatLon only handled Point in
EPSG:4326. Extend it to compute the outer-ring centroid for
Polygon/MultiPolygon and reproject 3857→4326 (frontend math, no backend
change), so the 10+ connection points render as markers with popups.
- Map vs table coverage mismatch: the table counts "В 2 км" while the OSM
utility-infrastructure layer fetched only 500 m (1 object inside 500 m vs
153 within 2 km). Raise the hook default to a shared
UTILITY_COVERAGE_RADIUS_M = 2000 so the map matches the table column.
- Coherence microcopy: clarify that the map shows the same networks as the
table (2 km), plus NSPD connection points and protection zones.
Adds unit tests for extractLatLon polygon-centroid + 3857→4326 reprojection.
Refs #1961
