fix(ingress): correct Authentik forward-auth service namespace

- Change middleware address from authentik-server.services.svc.cluster.local
  to authentik-server.authentik.svc.cluster.local (Authentik lives in
  authentik namespace, not services)
- Create ExternalName service authentik-server in services namespace so
  the rs-auth Ingress can route to the cross-namespace service

Build: no build needed

4-Infrastructure/k3s-flake/manifests/ingress/middleware.yaml

@@ -18,7 +18,7 @@ metadata:
   namespace: services
 spec:
   forwardAuth:
-    address: http://authentik-server.services.svc.cluster.local/outpost.goauthentik.io/auth/traefik
+    address: http://authentik-server.authentik.svc.cluster.local/outpost.goauthentik.io/auth/traefik
     authResponseHeaders:
       - X-Authentik-Username
       - X-Authentik-Email