Adds a useServerCapabilities hook that fetches /api/v1/health once per
session (staleTime: Infinity) and extracts the infrastructureEndpoints
flag. buildAdminTreeNodes now accepts an opts parameter so ClickHouse
and Database tabs are hidden when the server reports infra endpoints as
disabled. LayoutShell wires the hook result into the admin tree memo.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
