fix: CreateCheck uses type "check" not "check_def"

FK violation — entity_types table has name "check" but
phase3.go:320 was inserting type "check_def" causing:
entities_type_fkey (SQLSTATE 23503)

internal/httpapi/phase3.go

@@ -317,7 +317,7 @@ func (s *Server) CreateCheck(ctx context.Context, req gen.CreateCheckRequestObje
 	entity, err := q.InsertEntity(ctx, sqlcgen.InsertEntityParams{
 		ID:         id,
 		Slug:       slug,
-		Type:       "check_def",
+		Type:       "check",
 		Name:       slug,
 		Attributes: []byte("{}"),
 	})