Render forward zones into named.conf on every pod

type:forward zones are pure configuration (conditional forwarding), not
replicated data, so a resolver needs them on all pods. They were being
rndc-addzone'd on the primary only, so queries hitting a secondary pod
missed the forwarding. Render them into named.conf instead.

- render forward zones inside their view (or top-level when no views)
- BindCluster lists type:forward zones and watches BindZone to re-render
- BindZone controller skips forward zones (config-managed, no addzone)
- unit test for forward-zone-in-view rendering

internal/bind/render.go

@@ -16,6 +16,10 @@ type RenderInput struct {
 	Policies       []bindv1alpha1.BindPolicy
 	DNSSECPolicies []bindv1alpha1.BindDNSSECPolicy
 	Catalog        *bindv1alpha1.BindCatalogZone
+	// Forwards are type:forward BindZones. They are pure configuration (no
+	// replicated data), so they are rendered into named.conf on every pod
+	// rather than added dynamically to the primary.
+	Forwards []bindv1alpha1.BindZone
 	// PrimaryAddress is the in-cluster address secondaries transfer from.
 	PrimaryAddress string
 }
@@ -90,6 +94,29 @@ func render(in RenderInput, isPrimary bool) string {
 		b.WriteString(renderCatalogZoneDecl(in, isPrimary, ""))
 	}
 
+	// Top-level forward zones (BIND only allows top-level zones when no views
+	// are defined; in-view forward zones are rendered inside renderView).
+	if len(in.Views) == 0 {
+		for _, z := range in.Forwards {
+			if z.Spec.ViewRef == "" {
+				b.WriteString(renderForwardZone(z, ""))
+			}
+		}
+	}
+
+	return b.String()
+}
+
+// renderForwardZone renders a type:forward zone clause.
+func renderForwardZone(z bindv1alpha1.BindZone, indent string) string {
+	var b strings.Builder
+	b.WriteString(fmt.Sprintf("%szone \"%s\" {\n", indent, z.Spec.ZoneName))
+	b.WriteString(indent + "    type forward;\n")
+	b.WriteString(indent + "    forward only;\n")
+	if len(z.Spec.Forwarders) > 0 {
+		b.WriteString(fmt.Sprintf("%s    forwarders { %s };\n", indent, terminate(z.Spec.Forwarders)))
+	}
+	b.WriteString(indent + "};\n")
 	return b.String()
 }
 
@@ -122,6 +149,12 @@ func renderView(v bindv1alpha1.BindView, in RenderInput, isPrimary bool) string
 	if in.Catalog != nil {
 		b.WriteString(renderCatalogZoneDecl(in, isPrimary, "    "))
 	}
+	// Forward zones bound to this view.
+	for _, z := range in.Forwards {
+		if z.Spec.ViewRef == v.Name {
+			b.WriteString(renderForwardZone(z, "    "))
+		}
+	}
 	b.WriteString("};\n\n")
 	return b.String()
 }