vad: add missing control-interface namespace

apps/control-interface/base has no namespace.yaml (unlike reviews,
remarks, auth-flow), so Flux failed applying the HelmRelease into a
namespace that was never created.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/control-interface/vad/kustomization.yaml

@@ -2,3 +2,4 @@ apiVersion: kustomize.config.k8s.io/v1beta1
 kind: Kustomization
 resources:
   - ../base
+  - namespace.yaml

apps/control-interface/vad/namespace.yaml

@@ -0,0 +1,6 @@
+apiVersion: v1
+kind: Namespace
+metadata:
+  name: control-interface
+  labels:
+    istio-injection: enabled