refactor(system-info): reduce to Stripe-style status page

Reduce admin/system-info to a single focused status view: overall
status banner, components list from existing health checks, and an
environment meta table. Drops the Modules and Permissions tabs —
those were dev-diagnostics already available via CLI.

- Remove SystemInfoService + its test; wire the action directly to
  SystemHealthService and build meta inline
- Extend SystemHealthService with per-check label + description so
  the UI speaks in customer terms while the CLI doctor path stays
  compatible
- Rebuild the view on existing app-stats-table + app-empty-state
  primitives; add a small app-status-banner component for the
  headline signal
- Align help-center nav label and i18n keys (de/en)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

modules/help-center/templates/aside-help-panel.phtml

@@ -37,7 +37,7 @@ $helpNavGroups = [
         'icon' => 'bi-info-circle',
         'items' => [
             [
-                'label' => t('System info'),
+                'label' => t('System status'),
                 'path' => 'admin/system-info',
                 'active' => navActive('admin/system-info', true),
                 'visible' => $canViewSystemInfo,