feat: add governed Mol nature value layer

docs/DATA_SPECIFICATION.md

@@ -213,6 +213,21 @@ series may not be merged into one area-wide value. Point water level and
 discharge may not be converted to water volume without governed compatible
 depth/profile data.
 
+### BWK and Natura 2000 polygons
+
+The governed state-2025 import uses `BWK:Bwkhab` polygons. Geometry is fetched
+in EPSG:4326, validated and clipped against the persisted Mol boundary in
+EPSG:31370, then persisted in EPSG:4326. Required retained fields include
+`EVAL`, `EENH1..8`, `V1..3`, `HERK`, `BWKLABEL`, `HAB1..5`, `PHAB1..5`,
+`HERKHAB`, `HERKPHAB` and `HABLEGENDE`.
+
+BWK value classes remain independent. Natura 2000 codes, regionally important
+biotope codes and uncertain `ohab` knowledge gaps are also independent. PHAB
+shares can be theoretical source allocations; derived hectares therefore keep
+an estimate warning, especially for partial rectangle intersections. State
+2025 is a product edition and must not be presented as a uniform 2025 field
+survey or an annual time series.
+
 ### Vector
 
 Ondersteund: