Faster, gapless Kura cache on bare-metal infrastructure

The Kura build cache is now served from bare-metal infrastructure (Scaleway Dedibox and OVH) instead of Hetzner cloud VMs, delivering faster cache reads and writes through dedicated network bandwidth and local NVMe storage rather than shared cloud NICs and network-attached storage. Cache regions also deploy gaplessly, so the cache stays available during rolling infrastructure updates instead of dropping traffic during node replacement. A new ca-east region is being validated on OVH for staging and canary environments.