fix: file extension restriction doesn't check for dot

[timakai]

What?

Add a dot . in front of the checked extension before validating.

Why?

The current file restriction checker checks for extensions by checking the end of the filename.

file.name.toLowerCase().endsWith(ext)

It does not check if a dot is present, which gives problems with files that have no extension at all.
I uploaded a file with the name 0a621d9d1aa24f8ca3a5fbd523f6a24174061deb (a md5 hash). This file triggered the deb restriction because it ended in deb.

How?

Before:

const hasRestrictedExt = type.extensions.some((ext) => file.name.toLowerCase().endsWith(ext))

After:

const hasRestrictedExt = type.extensions.some((ext) => file.name.toLowerCase().endsWith("." + ext))