Remove nessus from cluster configuration

Remove all nessus references: ArgoCD project destination, Istio ambient
enrollment, waypoint gateway, authorization policies, ext-authz policy,
TLS certificate, ingress gateway host, Kyverno exclusion, and Authentik
forward-auth blueprint.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

infrastructure/istio/manifests/mesh/ext-authz-policies.yaml

@@ -119,21 +119,3 @@ spec:
         - operation:
             hosts:
               - scylla-manager.kube.huskypup.net
----
-# --- Nessus: Require Authentik auth ---
-# NOTE: Namespace 'nessus' must exist before applying this policy.
-# This policy will be skipped if the namespace doesn't exist yet.
-apiVersion: security.istio.io/v1
-kind: AuthorizationPolicy
-metadata:
-  name: ext-authz-nessus
-  namespace: nessus
-spec:
-  action: CUSTOM
-  provider:
-    name: authentik-ext-authz
-  rules:
-    - to:
-        - operation:
-            hosts:
-              - nessus.kube.huskypup.net