fix: populate ldns submodule and add autotools to LDNS build stage

- Re-cloned zonemaster-ldns with --recurse-submodules so the bundled
  ldns C library source (including Changelog and configure.ac) is present
- Added autoconf, automake, libtool to Dockerfile.backend ldns-build stage
  so libtoolize + autoreconf can generate ldns/configure during make

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

zonemaster-ldns/ldns/contrib/python/examples/python3/ldns-axfr.py

@@ -0,0 +1,56 @@
+#!/usr/bin/python
+# vim:fileencoding=utf-8
+#
+# AXFR client with IDN (Internationalized Domain Names) support
+#
+
+import ldns
+import encodings.idna
+
+def utf2name(name):
+    return '.'.join([encodings.idna.ToASCII(a).decode("utf-8") for a in name.split('.')])
+def name2utf(name):
+    return '.'.join([encodings.idna.ToUnicode(a) for a in name.split('.')])
+
+
+resolver = ldns.ldns_resolver.new_frm_file("/etc/resolv.conf")
+
+#addr = ldns.ldns_get_rr_list_addr_by_name(resolver, "zone.nic.cz", ldns.LDNS_RR_CLASS_IN, ldns.LDNS_RD);
+addr = resolver.get_addr_by_name("zone.nic.cz", ldns.LDNS_RR_CLASS_IN, ldns.LDNS_RD);
+if (not addr):
+    raise Exception("Can't retrieve server address")
+
+print("Addr_by_name:",str(addr).replace("\n","; "))
+
+#remove all nameservers
+while resolver.pop_nameserver(): 
+    pass
+
+#insert server addr
+for rr in addr.rrs():
+    resolver.push_nameserver_rr(rr)
+
+#AXFR transfer
+status = resolver.axfr_start(utf2name("háčkyčárky.cz"), ldns.LDNS_RR_CLASS_IN)
+if status != ldns.LDNS_STATUS_OK:
+    raise Exception("Can't start AXFR. Error: %s" % ldns.ldns_get_errorstr_by_id(status))
+
+#Print results
+while True:
+    rr = resolver.axfr_next()
+    if not rr: 
+        break
+
+    rdf = rr.owner()
+    if (rdf.get_type() == ldns.LDNS_RDF_TYPE_DNAME):
+        print("RDF owner: type=",rdf.get_type_str(),"data=",name2utf(str(rdf)))
+    else:
+        print("RDF owner: type=",rdf.get_type_str(),"data=",str(rdf))
+    print("   RR type=", rr.get_type_str()," ttl=",rr.ttl())
+    for rdf in rr.rdfs():
+        if (rdf.get_type() == ldns.LDNS_RDF_TYPE_DNAME):
+            print("   RDF: type=",rdf.get_type_str(),"data=",name2utf(str(rdf)))
+        else:
+            print("   RDF: type=",rdf.get_type_str(),"data=",str(rdf))
+
+    print()