Improve layout on the login page

Improvement of the layout of the dialog list on the login page.

HOW TO GO TO LOGIN PAGE:

• Log in to bwsync&share and then click on "Mitglied im bwSync&Share Verbund"

TO BE IMPROVED

• Adjust size and position of ::before psuedo element (arrow)
• Add list border and background
• Display the scrollbar all the time when it is needed