Improve handling of signatures that lead to a large number of false-positives

We use clamav to scan uploaded extensions for malware.

The signatures used to detect them is automatically updated and taken from the official source.

If there are signatures included that trigger a lot of false-positives, we currently do not have a way to flag them or exclude them from scanning.

We need to improve our handling of such cases. Possible options are:

- hard exclude certain signatures
- limit the file types certain signatures apply to
- lower severity of certain signatures to not automatically put extensions in quarantine

Start by locating the TypeScript code that invokes ClamAV, processes automatically updated signatures, and quarantines extensions. Compare the three listed handling options with the current scan flow; this issue is done only when a specific policy is selected and its false-positive behavior is covered by the project’s relevant tests.

Written by the indexing model from the issue text.