Fix netbird-operator namespace reference in istio mesh policies

allow-netbird-operator-access (AuthorizationPolicy) and the netbird-operator
PeerAuthentication both targeted namespace 'netbird-operator', which has
never existed - the actual netbird-operator pod runs in the 'netbird'
namespace. This permanently blocked istio-mesh-config from going Synced
(kubectl apply failed: namespaces "netbird-operator" not found on every
sync attempt).

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

infrastructure/istio/manifests/mesh/peer-authentication-webhooks.yaml

@@ -23,11 +23,13 @@ spec:
     mode: PERMISSIVE
 ---
 # Netbird operator webhook receives calls from the API server
+# (namespace is "netbird", not "netbird-operator" - that namespace
+# doesn't exist; fixed 2026-08-17)
 apiVersion: security.istio.io/v1
 kind: PeerAuthentication
 metadata:
   name: allow-apiserver-webhooks
-  namespace: netbird-operator
+  namespace: netbird
 spec:
   mtls:
     mode: PERMISSIVE