Apply the same user filter to every page of account members

Administrators see banned users in the account settings, but only the
first page counted them: the next pages listed active users alone. A
banned member before the page boundary shifted the offset, so one active
member was never listed. Both pages now share User.visible_to.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0142qgjggdJ2KDdGk7RF9Xm9

app/models/user/bannable.rb

@@ -1,6 +1,11 @@
 module User::Bannable
   extend ActiveSupport::Concern
 
+  included do
+    # Administrators still see banned users, so they can lift the ban.
+    scope :visible_to, ->(user) { user.can_administer? ? where(status: %i[ active banned ]) : active }
+  end
+
   def ban
     transaction do
       create_bans_from_sessions