Fixed Apple Silicon runners on Scaleway hanging when remote module cache became unreachable

Fixed a Scaleway networking issue that could make the runner-cache node lose its Private Network address, causing macOS CI builds to hang at “Fetching remote binaries via module cache” with long timeouts. The node now discovers the address once via DHCP and holds it statically, so remote module cache access stays reliable across reboots and DHCP lease churn.