fix: accept bare Pi-hole IPv4 addresses

internal/pihole/client_test.go

@@ -101,6 +101,10 @@ func TestNewValidatesAndNormalizesPiHoleURL(t *testing.T) {
 	if err != nil || client.BaseURL() != "http://pihole.local/custom/api" {
 		t.Fatalf("custom path not normalized: %q err=%v", client.BaseURL(), err)
 	}
+	client, err = New("10.0.20.100", false)
+	if err != nil || client.BaseURL() != "http://10.0.20.100/api" {
+		t.Fatalf("bare IPv4 address not normalized: %q err=%v", client.BaseURL(), err)
+	}
 	for _, invalid := range []string{"pi.hole", "ftp://pi.hole", "https://user:pass@pi.hole", "https://pi.hole?sid=secret"} {
 		if _, err := New(invalid, false); err == nil {
 			t.Errorf("invalid URL accepted: %s", invalid)