feat(webapp): reach the account menu from the collapsed side menu

When the side menu is collapsed the standalone account button is hidden, so the
account actions (Profile, Personal Access Tokens, Security, Logout, and the
admin/impersonation entries) were only reachable by expanding the menu first.

Surface them on the collapsed rail: the org popover (the one menu always
reachable when collapsed) now shows an "Account" item at the top, divided from
the org items, that opens the full account menu as a submenu.

To keep it maintainable the account entries are extracted into a shared
AccountMenuItems component used by both the standalone account popover and the
submenu, and the hover submenu behind Switch organization and Integrations is
generalized into a shared SideMenuPopoverSubMenu, so new nested menus and
account entries are easy to add in one place.

Author: samejr