Fix colors of feedback list in dark mode

[MizukiTemma]

Short description

This PR fixes the color conflict, which is a side effect of #515

Proposed changes

• Introduce a new color assignment to feedback list in the dark mode

🤔 The contrast between "bold" and "normal" fonts is sadly not really visible enough in the dark mode (I can only slightly tell whether bold or normal). Should we use different font colors depend on the status (read/unread)? @hauf-toni

This is how it looks after fix with this PR.

Resolved issues

Fixes: #532