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.