Add typed API wrappers (api/logs.ts, api/troubleshoot.ts) and two new
screens: LogsScreen (paged, level-badged, server-side filtered log table)
and TroubleshootingScreen (General JSON viewer with copy, plus per-platform
NVIDIA/QSV/VAAPI/VideoToolbox capability tabs when populated). Both are
registered under a new "System" nav group in App.tsx alongside Settings.
Settings' Classic UI help text and About card now point at the new screens
instead of the Blazor logs/troubleshooting pages.
