Add tab navigation (Services, Bookmarks, Settings)

- Services tab: shows all internal services with health status
- Bookmarks tab: shows all external bookmarks by category
- Settings tab: dark mode toggle and portal info
- Running services counter in header
- Consistent tab styling with underline indicator

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/components/Icons.tsx

@@ -106,6 +106,7 @@ export const icons: Record<string, React.ComponentType<IconProps>> = {
   'external-link': createIcon('<path d="M15 3h6v6"/><path d="M10 14 21 3"/><path d="M18 13v6a2 2 0 0 1-2 2H5a2 2 0 0 1-2-2V8a2 2 0 0 1 2-2h6"/>'),
   'refresh-cw': createIcon('<path d="M3 12a9 9 0 0 1 9-9 9.75 9.75 0 0 1 6.74 2.74L21 8"/><path d="M21 3v5h-5"/><path d="M21 12a9 9 0 0 1-9 9 9.75 9.75 0 0 1-6.74-2.74L3 16"/><path d="M8 16H3v5"/>'),
   'x': createIcon('<path d="M18 6 6 18"/><path d="m6 6 12 12"/>'),
+  'settings': createIcon('<path d="M12.22 2h-.44a2 2 0 0 0-2 2v.18a2 2 0 0 1-1 1.73l-.43.25a2 2 0 0 1-2 0l-.15-.08a2 2 0 0 0-2.73.73l-.22.38a2 2 0 0 0 .73 2.73l.15.1a2 2 0 0 1 1 1.72v.51a2 2 0 0 1-1 1.74l-.15.09a2 2 0 0 0-.73 2.73l.22.38a2 2 0 0 0 2.73.73l.15-.08a2 2 0 0 1 2 0l.43.25a2 2 0 0 1 1 1.73V20a2 2 0 0 0 2 2h.44a2 2 0 0 0 2-2v-.18a2 2 0 0 1 1-1.73l.43-.25a2 2 0 0 1 2 0l.15.08a2 2 0 0 0 2.73-.73l.22-.39a2 2 0 0 0-.73-2.73l-.15-.08a2 2 0 0 1-1-1.74v-.5a2 2 0 0 1 1-1.74l.15-.09a2 2 0 0 0 .73-2.73l-.22-.38a2 2 0 0 0-2.73-.73l-.15.08a2 2 0 0 1-2 0l-.43-.25a2 2 0 0 1-1-1.73V4a2 2 0 0 0-2-2z"/><circle cx="12" cy="12" r="3"/>'),
   'loader': createIcon('<path d="M12 2v4"/><path d="m16.2 7.8 2.9-2.9"/><path d="M18 12h4"/><path d="m16.2 16.2 2.9 2.9"/><path d="M12 18v4"/><path d="m4.9 19.1 2.9-2.9"/><path d="M2 12h4"/><path d="m4.9 4.9 2.9 2.9"/>'),
 };