Do we really need /mnt permissions?

Hi,
OpenCode requires these permissions:

```
- --filesystem=/media
- --filesystem=/mnt
- --filesystem=/run/media
```

I removed these permissions on my end, and everything works as expected, even with projects running from a USB stick.
I guess that if we can remove them, it would help clean up some scary nonsense on Flathub. Like this one:

Review the app's Flatpak permission declarations for /media, /mnt, and /run/media, then verify whether projects on USB storage still work without them. Done means unnecessary permissions are removed while those project scenarios continue to function; confirm any remaining edge cases in the issue thread.

Vom Indexierungsmodell aus dem Issue-Text verfasst.