votes: allow Members to vote.

* Allow Member-level users to vote.
* Don't allow Banned or Restricted users to create favorites any more.

Banned and Restricted users aren't allowed to upvote or favorite any
more to prevent sockpuppet accounts from upvoting even after they're
banned.

test/factories/user.rb

@@ -8,6 +8,7 @@ FactoryBot.define do
     factory(:banned_user) do
       transient { ban_duration {3} }
       is_banned {true}
+      active_ban factory: :ban
     end
 
     factory(:restricted_user) do