DNS blocklists asked in the background, verdicts kept (closes #104)

Work in progress.

Model: opus-5-5

internal/reputation/export_test.go

@@ -1,9 +1,27 @@
 package reputation
 
-import "net/http"
+import (
+	"context"
+	"net"
+	"net/http"
+	"net/netip"
+)
 
 // SetTransport has l's fetches go through transport instead of the
 // network.
 func (l *Lists) SetTransport(transport http.RoundTripper) {
 	l.httpClient.Transport = transport
 }
+
+// SetDial has d's queries go through dial instead of the network.
+func (d *DNSBL) SetDial(
+	dial func(ctx context.Context, network, address string) (net.Conn, error),
+) {
+	d.resolver = &net.Resolver{PreferGo: true, Dial: dial}
+}
+
+// LookUp asks zone about addr at once, as a query in the background does,
+// and returns whether zone lists addr.
+func (d *DNSBL) LookUp(zone string, addr netip.Addr) (bool, error) {
+	return d.lookUp(context.Background(), query{zone: zone, client: addr})
+}