Fix bare-metal Kura regions by using the shared regional gateway

Hosted Kura builds on the bare-metal eu-central region now actually serve traffic. Previously, every dedicated account was assigned its own host-network ingress controller, two of which could not both bind port 443 on the same box, so the dedicated gateway sat unschedulable and the account’s KuraInstance (pinned to its dedicated ingress class) never became reachable, even though the platform’s shared gateway was healthy. The server now routes bare-metal accounts onto the region’s shared ingress class served by the platform gateway. Dedicated accounts on LoadBalancer-backed regions keep their own dedicated gateway as before. Already-provisioned instances in the broken state recover through a Destroy -> Deploy.