marreta: content-cleaning proxy on Dankclaw, gluetun netns, guard-chained

Deploy manualdousuario/marreta (Laravel / serversideup php:8.4-fpm-nginx)
as a rootless Quadlet pair (marreta + marreta-browser/Lightpanda), both
joining gluetun's netns so all fetch egress exits the same ProtonVPN
tunnel as SearXNG.

- marreta relocated to NGINX_HTTP_PORT=8085 (netns already has searxng on
  8080); gluetun publishes 8082:8085; Caddy dials 192.168.0.143:8082.
- Guard chain: marreta.franksdank.cloud -> Anubis :8923 -> Authentik ->
  post-auth :8017 @marreta -> 8082. Access = any authenticated user.
- Secrets seeded to /home/dank/Containers/marreta/env (0600) from
  MARRETA_APP_KEY / MARRETA_ADMIN_EMAIL / MARRETA_ADMIN_PASSWORD.
- deploy-plan.py: marreta joins the gluetun netns family.
- New seam tests/marreta_quadlet.bats (17 contracts); scoping test updated
  for the widened netns family. Doc: Dankclaw/Marreta.md + index + log.

dankclaw/searxng/quadlet/gluetun.container

@@ -29,6 +29,7 @@ Environment=WIREGUARD_ENDPOINT_PORT=${WIREGUARD_ENDPOINT_PORT}
 Environment=WIREGUARD_ALLOWED_IPS=${WIREGUARD_ALLOWED_IPS}
 Environment=WIREGUARD_PERSISTENT_KEEPALIVE_INTERVAL=${WIREGUARD_PERSISTENT_KEEPALIVE_INTERVAL}
 PublishPort=8081:8080
+PublishPort=8082:8085
 
 [Service]
 EnvironmentFile=/opt/searxng/.env