Pages: All pages when logged in

Expected behavior: When logged in, selecting the user icon brings up a menu that complies with the styles in OOUI (ButtonMenuSelectWidget (clearOnSelect=false, menu.horizontalPosition="end"))

Observed behavior: User menu uses different styles (background color, font size, font justification, padding, etc). Note that this task is scoped only to the user menu since it's the most important menu for the initial launch. However, if changes all dropdown menu styles is easier, that also works.