[client] Support disable search domain for custom zones (#4826)

Two new boolean flags, SearchDomainDisabled and SkipPTRProcess, are added to CustomZone and its protobuf; they are propagated through the engine to DNS host logic. Host matching now uses SearchDomainDisabled directly, and PTR collection skips zones with SkipPTRProcess; reverse zones are initialized with SearchDomainDisabled: true.

client/internal/engine.go

@@ -1207,7 +1207,9 @@ func toDNSConfig(protoDNSConfig *mgmProto.DNSConfig, network netip.Prefix) nbdns
 
 	for _, zone := range protoDNSConfig.GetCustomZones() {
 		dnsZone := nbdns.CustomZone{
-			Domain: zone.GetDomain(),
+			Domain:               zone.GetDomain(),
+			SearchDomainDisabled: zone.GetSearchDomainDisabled(),
+			SkipPTRProcess:       zone.GetSkipPTRProcess(),
 		}
 		for _, record := range zone.Records {
 			dnsRecord := nbdns.SimpleRecord{