Self-hosting docs corrected for Kura routing, peer TLS, and single-node setup

The self-hosting guides have been corrected to match current server behavior. CLI cache endpoint routing on a self-hosted server is documented as driven by the global TUIST_CACHE_ENDPOINTS (Helm server.cacheEndpointUrl), not the unused TUIST_KURA_ENDPOINTS / server.kuraEndpointUrls. Node registration on a self-hosted server is clarified as dashboard-only, since routing comes from TUIST_CACHE_ENDPOINTS. Peer mTLS (KURA_INTERNAL_TLS_*) is documented as multi-node only; a single node uses an http:// KURA_NODE_URL with peer TLS off, and only the scheme changes to http (the host and KURA_INTERNAL_PORT are unchanged). The Cache page is also documented as available by default on a self-hosted server, removing the prior /ops/flags workaround.