Kura cache surface available by default on self-hosted servers

Self-hosted Tuist servers now expose the Cache page, its sidebar entry, the Usage page entry, and the account-settings section by default. Operators no longer have to reach /ops/flags and flip the :kura feature flag before they can generate the control-plane credential, since the self-hosted-cache entitlement is already granted on a self-hosted deployment. On a self-hosted server the Cache page now shows only credential generation and the registered-nodes list; the managed cache-server provisioning UI (which is inert without Tuist-managed regions or Kubernetes) is hidden when there are no servers or available regions. The hosted tuist.dev server is unchanged and remains gated behind the :kura toggle.