Download files

[kkuepper]

• [ ] implement download functionality (url is on track.media.files.url. Take first of array)
• [ ] show popup when trying to download a message (see figma)
• [ ] don't show popup if user has Download permission
• [ ] hide download button on Electron

This isn't strictly relevant for Public release. We could just hide the download button.

The text in Figma is outdated: headline: Download of messages unavailable text: The ability to download messages from BMM is no longer available. If you need a message for a specific use, please contact us and explain your needs. support mail: mailto:support@bcc.media

[kkuepper]

I decided against implementing the download action, since we're considering removing it at some point anyway. Because of that it shouldn't be one of the quick actions. So I use "AddToPlaylist" instead as quick action. Also downloading in Electron doesn't really feel right. We should still implement it for the website though.