Status (services, PHP env, disk) is now always visible above the log/config
tab bar rather than being one of the tab targets:
- Status section rendered unconditionally above <nav class="sys-tabs">.
- Services grid, PHP info grid and disk bar grouped inside a collapsible
<section> with a header row containing the cache-freshness badge and a
toggle button (▲ Réduire / ▼ Développer).
- Collapse state persisted in localStorage so the preference survives
page reloads (e.g. when switching log tabs).
- Tab bar now only contains the three log tabs + nginx config; the 'Statut'
tab is removed. Legacy ?tab=status URLs fall through to nginx_access.
- PHP/disk sub-sections laid out in a 2-col grid inside the status panel;
responsive single-col below 700px.
- system.css: new .sys-status-section / .sys-status-header /
.sys-status-toggle / .sys-status-meta rules added.
- aria-current="page" added to active tab links.
- todo/03-system-cache.md: all items marked done; notes added explaining
why log caching was deliberately omitted.
