List of issues found with dark mode

[nico3333fr]

Please centralize here issues found with Dark mode

[DeepSpaceHarbor]

• [x] The colors have white outline

[DeepSpaceHarbor]

• [x] The hover style when selecting contact.

[matej-n]

• [x] The color of the text on a thread of new messages is white on white background:

[econdepe]

• [x] The merge button only looks like a button when hovering over:

[nico3333fr]

All issues actually found have been fixed. Closing.