Fix Devise mapping not found error in Rails 8

This fixes a Devise mapping error on system tests.

```
E

Error:
AdminUsersTest#test_visiting_the_edit:
RuntimeError: Could not find a valid mapping for #<AdminUser id: 1, email: [FILTERED], created_at: "2025-09-25 21:07:53.971537000 +0000", updated_at: "2025-09-25 21:07:53.971537000 +0000">
    test/system/active_admin/admin_users_test.rb:42:in 'block in <class:AdminUsersTest>'

bin/rails test test/system/active_admin/admin_users_test.rb:41
```

Author: javierjulio

test/application_system_test_case.rb

@@ -4,4 +4,10 @@
 
 class ApplicationSystemTestCase < ActionDispatch::SystemTestCase
   driven_by :selenium, using: :headless_chrome, screen_size: [1400, 1400]
+
+  def setup
+    # Fix Devise mapping not found error in Rails 8 when running these spec types directly
+    # https://github.com/heartcombo/devise/issues/5774#issuecomment-2944728967
+    Rails.application.try(:reload_routes_unless_loaded)
+  end
 end