Add troubleshooting note for the Linux tray icon (#60)

Author: danbarr

docs/toolhive/guides-ui/install.mdx

@@ -227,6 +227,33 @@ If the retry button doesn't work, try restarting ToolHive.
 
 </details>
 
+<details>
+<summary>No system tray icon on Linux</summary>
+
+Recent versions of Fedora Linux and other distributions have removed the
+AppIndicator extension from their default installations. ToolHive requires this
+extension for the system tray icon to work properly.
+
+On Fedora, install the `gnome-shell-extension-appindicator` package:
+
+```bash
+sudo dnf install gnome-shell-extension-appindicator
+```
+
+You'll need to log out and log back in to activate the extension.
+
+Alternatively, install the
+[Extension Manager](https://github.com/mjakeman/extension-manager) app. It's
+available as a native package in many distributions, or you can install it from
+[Flathub](https://flathub.org/apps/com.mattjakeman.ExtensionManager). Then, use
+Extension Manager to install the
+[AppIndicator](https://extensions.gnome.org/extension/615/appindicator-support/)
+extension (listed as "AppIndicator and KStatusNotifierItem Support").
+
+The ToolHive icon should now appear in your system tray.
+
+</details>
+
 ### Other issues
 
 For other installation issues, check the