Remove nessus app and fix envoy-gateway OCI chart bug

- Delete nessus Application CRD, manifests, and bootstrap script
- Vendor envoy-gateway Helm chart (v1.6.3) locally to work around
  ArgoCD v3.3.3 Docker Hub OCI resolution bug
- Re-enable auto-sync for envoy-gateway

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

charts/envoy-gateway/templates/NOTES.txt

@@ -0,0 +1,20 @@
+**************************************************************************
+*** PLEASE BE PATIENT: Envoy Gateway may take a few minutes to install ***
+**************************************************************************
+
+Envoy Gateway is an open source project for managing Envoy Proxy as a standalone or Kubernetes-based application gateway.
+
+Thank you for installing Envoy Gateway! 🎉
+
+Your release is named: {{ .Release.Name }}. 🎉
+
+Your release is in namespace: {{ .Release.Namespace }}. 🎉
+
+To learn more about the release, try:
+
+  $ helm status {{ .Release.Name }} -n {{ .Release.Namespace }}
+  $ helm get all {{ .Release.Name }} -n {{ .Release.Namespace }}
+
+To have a quickstart of Envoy Gateway, please refer to https://gateway.envoyproxy.io/latest/tasks/quickstart.
+
+To get more details, please visit https://gateway.envoyproxy.io and https://github.com/envoyproxy/gateway.