Add host info views and network error handling

Introduce modular host info UI components: Header, InfoRow,
CopyButton, and Browser/Local/Public views. Refactor ServerInfo to
compose these components.

Add network error handling: background listens for webRequest
onErrorOccurred and forwards errors to Tab.handleError. Implement
Tab.handleError to store friendly error info and Tab.processSystemPage
to handle browser/system pages.

components/Error.tsx

@@ -7,6 +7,7 @@ export default function Error({ error }: { error: string }) {
         <ExclamationTriangleIcon className="w-6 h-6 text-red-600 dark:text-red-400" />
       </div>
       <h3 className="text-sm font-bold text-gray-900 dark:text-white mb-1">Unable to Load</h3>
+      <p className="text-sm text-gray-500 dark:text-gray-400">{error}</p>
     </div>
   );
 }