Firefox addon on Android prevents user leaving from addon's UI

### Describe the Bug

Hoarder's addon on Firefox on Android does not let user to leave from the addon's UI after adding a site to Hoarder. Back buttons (both on the addon and Android's own back button) just keep reloading the UI.

Hitting back button rapidly enough does help though, but then you might end up going back in browsing history accidentally.

See attached video:
https://github.com/user-attachments/assets/7a3228ad-2f8d-42e7-8133-6931f1d1fd03

### Steps to Reproduce

1. Install Hoarder's addon from Firefox's addons menu
2. Configure it to use your Hoarder service
3. Open a page you want to add
4. Poke Hoarder's addon entry in browser's menu
5. Try to back to out from Hoarder's UI once done

### Expected Behaviour

Hitting back button should close Hoarder addon's UI.

### Screenshots or Additional Context

_No response_

### Device Details

Android's Firefox 133.0.3

### Exact Hoarder Version

0.20.0

### Have you checked the troubleshooting guide?

- [X] I have checked the troubleshooting guide and I haven't found a solution to my problem

Start by reproducing the addon's UI flow from the browser menu on Android's Firefox 133.0.3, then inspect the Firefox addon entry point responsible for back-button handling. Done means the addon's UI closes with both its back button and Android's back button without reloading or changing browsing history; verify the behavior against version 0.20.0.

Written by the indexing model from the issue text.