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>

web/css/core.css

@@ -28,6 +28,7 @@
 @import url("components/app-list-titlebar.css");
 @import url("components/app-details-titlebar.css");
 @import url("components/app-dashboard-titlebar.css");
+@import url("components/app-status-banner.css");
 @import url("components/app-empty-state.css");
 @import url("components/app-details.css");
 @import url("components/app-details-card.css");