Make catalog zone name matching case-insensitive

DNS names are case-insensitive (RFC 4343), but the catalog-zone
dispatch compared dname verbatim:

    if dname == "catz" or dname == f"{nb_view.name}.catz":

dname is derived from qname.to_text(), which preserves the casing the
client sent. A query for CATZ, Public.catz, or any other mixed-case
variant failed the comparison and fell through to _get_zone_from_nb,
which returned None, so the request was denied instead of being served
as a catalog zone.

Lowercase both sides before comparing. Pass the lowercased name to
create_zone so catalog zones always get a canonical lowercase origin,
and pass the original dname to _get_zone_from_nb to leave the regular
zone-lookup behavior unchanged.

netbox_dns_bridge/request_handler.py

@@ -283,8 +283,9 @@ class DNSBaseRequestHandler(socketserver.BaseRequestHandler):
             return
 
         # Check if catalog zone
-        if dname == "catz" or dname == f"{nb_view.name}.catz":
-            zone = catzm.create_zone(dname, nb_view.name)
+        dname_lower = dname.lower()
+        if dname_lower == "catz" or dname_lower == f"{nb_view.name.lower()}.catz":
+            zone = catzm.create_zone(dname_lower, nb_view.name)
         else:
             zone = self._get_zone_from_nb(dname, nb_view.name)
         # When zone was not found, let client know