fix(dns): resolve CNAME chains and prevent invalid IP parsing

- Add automated in-band CNAME chain resolution to extract final A/AAAA IP addresses.
- Replace `MaxResponseAnswers` with `MaxIPs` and `MaxCNAMEs` to explicitly bound resource decoding and prevent memory exhaustion.
- Bound CNAME chain traversal to prevent infinite loops from cyclic records.

x/xnet/stack-async.go

@@ -629,8 +629,8 @@ func (s *StackAsync) StartLookupIPType(host string, qtype dns.Type) error {
 		Additional: []dns.Resource{
 			s.ednsopt,
 		},
-		EnableRecursion:    true,
-		MaxResponseAnswers: uint16(len(s.addrbufnip)),
+		EnableRecursion: true,
+		MaxIPs:          uint16(len(s.addrbufnip)),
 	})
 	if err != nil {
 		return err