fix(traefik): revert controllerName to default; drop invalid additionalArguments

Traefik v3.7.0 does not expose controllerName as a CLI flag or chart value.
Both GatewayClasses use the default traefik.io/gateway-controller so that
both Traefik instances (which also default to that name) will accept them.
Internal/external separation is handled by the existing labelSelector on
each provider.

apps/base/traefik-system/gatewayclass-external.yaml

@@ -4,4 +4,4 @@ kind: GatewayClass
 metadata:
   name: traefik-external
 spec:
-  controllerName: traefik.io/gateway-controller-external
+  controllerName: traefik.io/gateway-controller

apps/base/traefik-system/gatewayclass-internal.yaml

@@ -4,4 +4,4 @@ kind: GatewayClass
 metadata:
   name: traefik-internal
 spec:
-  controllerName: traefik.io/gateway-controller-internal
+  controllerName: traefik.io/gateway-controller