refactor: change Sidekiq route to admin/tasks

- Update route for Sidekiq web interface from '/sidekiq'
  to '/admin/tasks'

This change improves the coherence of the application's routing
by placing the Sidekiq interface under a more descriptive
namespace. It consolidates admin-related tasks under a common
path, enhancing the organization of the routing structure.

config/routes.rb

@@ -23,7 +23,7 @@ Rails.application.routes.draw do
 
   # mount Sidekiq::Web => '/sidekiq'
   authenticate :admin_user do
-    mount Sidekiq::Web => "/sidekiq"
+    mount Sidekiq::Web => "/admin/tasks"
   end
   # Define your application routes per the DSL in https://guides.rubyonrails.org/routing.html