Delete server-side session on logout

When it's set. Also, store it in current attributes for convenience.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/controllers/sessions_controller.rb

@@ -18,7 +18,7 @@ class SessionsController < ApplicationController
 
   def destroy
     remove_push_subscription
-    reset_authentication
+    terminate_current_session
     redirect_to root_url
   end