fix: identify BWK snapshot series

backend/tests/test_sprint204_bwk_natura2000.py

@@ -82,6 +82,7 @@ def test_official_bwk_contract_and_class_labels_are_fixed() -> None:
     assert module.WFS_URL == "https://geo.api.vlaanderen.be/BWK/wfs"
     assert module.TYPE_NAME == "BWK:Bwkhab"
     assert module.SOURCE_VERSION == "2025"
+    assert module.TEMPORAL_SERIES_KEY == "inbo-bwk-natura2000:mol"
     assert module.ATTRIBUTION == "Bron: INBO"
     assert module.EVALUATION_LABELS == {
         "z": "Biologisch zeer waardevol",