Query the GCVE BCP-07 KEV catalogs; deprecate the CISA KEV helpers.
Vulnerability-Lookup retires /api/cisa_kev/ (vulnerability-lookup#641):
that endpoint served a separate, non-BCP-07 mirror of the CISA list that
kept retracted entries. The CISA catalog, like ENISA's and the others, is a
GCVE BCP-07 KEV catalog served by /api/kev/, identified by its origin
UUID.