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/models/current.rb

@@ -1,8 +1,16 @@
 class Current < ActiveSupport::CurrentAttributes
-  attribute :user, :request
+  attribute :session, :user, :request
 
   delegate :host, :protocol, to: :request, prefix: true, allow_nil: true
 
+  def session=(value)
+    super(value)
+
+    if value.present?
+      self.user = session.user
+    end
+  end
+
   def account
     Account.first
   end