Console panel, collapsible panels, Add on the Members panel

- Server settings > Console sends a raw console command for staff with @css/rcon
  (POST /api/admin/rcon). It doesn't wait for the server; the output is only logged.
- Staff & ranks and Server settings panels fold up by clicking their heads. All but
  Ranks and Server start folded; a folded Ranks panel shows the selected rank.
- The Members panel has an Add button that opens Add staff with that rank picked.
- The public rank log shows a rank being given as Promoted and taken away as Demoted.

internal/web/server.go

@@ -112,6 +112,7 @@ func (s *Server) Handler() http.Handler {
 	admin("POST /api/admin/map", s.changeMap)
 	admin("POST /api/admin/restart", s.restartRound)
 	admin("POST /api/admin/reload-admins", s.reloadAdmins)
+	admin("POST /api/admin/rcon", s.rcon)
 	admin("POST /api/admin/groups", s.createGroup)
 	admin("PUT /api/admin/groups/{id}", s.updateGroup)
 	admin("DELETE /api/admin/groups/{id}", s.deleteGroup)