Thumbnail generation uses bandwidth when not in focus

[flo-st]

Describe the bug
When opening directories containing media files, the drive tries to create thumbnails.
These use all available bandwidth and continue to be created even if media is playing in the web drive, causing it to lag, or if the desktop client (3.0.39) was minimized after the directory was opened.

To Reproduce
Steps to reproduce the behavior:

1. Go to 'Cloud Drive'
2. Open a directory containing multiple media files
3. Notice that thumbnails are being created
4. Start playing a media file
5. Notice the lag when playing media
6. Stop playing media and minimize the desktop client
7. Notice that the bandwidth used for thumbnail generation persists

Expected behavior
The drive should not attempt to generate thumbnails when media is playing or when the desktop client is minimized.

Browser and OS (please complete the following information):

• OS: Windows 10
• Firefox 133.0
• No VPN/Proxy used

Additional context
The console logs multiple ServiceWorker errors when media is not supported for playback.