Fix authoritative secondary replication (TSIG transfer + stable primary)

Secondaries never replicated any member zone: the master's catalog zone
requires key-authenticated AXFR (allow-transfer { key "transfer-key"; }),
but the rendered secondary config transferred without presenting the key,
so every catalog transfer was REFUSED and no member zones provisioned.
Two further gaps compounded it: member zones had no allow-transfer at all,
and secondaries pointed at the primary's pod IP, which dies on restart.

- Render the catalog transfer key into the secondary catalog-zones
  default-primaries and the secondary catalog zone primaries, so
  key-authenticated AXFR from the primary is accepted.
- Add allow-transfer { key "<transfer-key>"; } to catalog member primary
  zones (when the zone does not set an explicit allow-transfer), so
  secondaries can pull them; applied to existing zones via modzone.
- Point secondaries at the stable primary Service ClusterIP instead of the
  primary pod IP, so replication survives primary pod restarts (falls back
  to the pod IP when no primary Service exists).

internal/bind/render_test.go

@@ -80,6 +80,24 @@ func TestRenderCatalogUsesPrimaryIP(t *testing.T) {
 	}
 }
 
+func TestRenderCatalogPrimariesCarryTransferKey(t *testing.T) {
+	// When the catalog declares a transfer key, secondaries must present it in
+	// both the catalog-zones default-primaries and the secondary catalog zone,
+	// or the key-authenticated primary REFUSES the AXFR.
+	in := RenderInput{
+		Cluster:        newCluster(bindv1alpha1.ModeAuthoritative),
+		Catalog:        &bindv1alpha1.BindCatalogZone{Spec: bindv1alpha1.BindCatalogZoneSpec{ZoneName: "catalog.internal", TransferKeyRef: "transfer-key"}},
+		PrimaryAddress: "10.43.0.5",
+	}
+	_, secondary := RenderNamedConf(in)
+	if !strings.Contains(secondary, `default-primaries { 10.43.0.5 key "transfer-key"; }`) {
+		t.Fatalf("catalog-zones default-primaries must carry the transfer key:\n%s", secondary)
+	}
+	if !strings.Contains(secondary, `primaries { 10.43.0.5 key "transfer-key"; }`) {
+		t.Fatalf("secondary catalog zone primaries must carry the transfer key:\n%s", secondary)
+	}
+}
+
 func TestRenderForwardZoneInView(t *testing.T) {
 	rec := true
 	in := RenderInput{