glitch-soc theme engine fixes for the challenges controller

app/controllers/auth/challenges_controller.rb

@@ -5,6 +5,7 @@ class Auth::ChallengesController < ApplicationController
 
   layout 'auth'
 
+  before_action :set_pack
   before_action :authenticate_user!
 
   skip_before_action :require_functional!
@@ -19,4 +20,10 @@ class Auth::ChallengesController < ApplicationController
       render_challenge
     end
   end
+
+  private
+
+  def set_pack
+    use_pack 'auth'
+  end
 end