Allow and deny lists per subnet; every option of a DHCP message in words

- A subnet is a deny-list subnet (the default: everyone not denied) or
  an allow-list subnet (only clients allowed or with a reservation);
  the deny list counts in both. Entries are MAC addresses, prefixes
  (aa:bb:cc:*) or client IDs. A refused client gets no answer (DENIED
  in the activity log, with an Allow button) or a NAK on renewal.
  steward access, the subnet's Access tab. Schema migration 7.
- The activity log keeps each message's header fields and options,
  decoded into words (dhcp4.Describe): the parameter request list by
  name, client IDs, lease times. ▸ on an Activity row, steward
  activity show N / --details, GET /events/{id}.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/server/h_config.go

@@ -238,6 +238,26 @@ func applySubnetInput(sn *model.Subnet, in *api.SubnetInput) error {
 	if in.AddressOrder != nil {
 		sn.AddressOrder = orderInput(*in.AddressOrder)
 	}
+	if in.Access != nil {
+		sn.Access = strings.ToLower(strings.TrimSpace(*in.Access))
+	}
+	for _, l := range []struct {
+		in  *[]model.ClientMatch
+		out *[]model.ClientMatch
+	}{{in.Allow, &sn.Allow}, {in.Deny, &sn.Deny}} {
+		if l.in == nil {
+			continue
+		}
+		list := []model.ClientMatch{}
+		for _, m := range *l.in {
+			norm, err := model.ParseClientMatch(m.Match)
+			if err != nil {
+				return badRequest("%v", err)
+			}
+			list = append(list, model.ClientMatch{Match: norm, Comment: strings.TrimSpace(m.Comment)})
+		}
+		*l.out = list
+	}
 	if in.LeaseTime != nil {
 		sn.LeaseTime = *in.LeaseTime
 	}