tons of changes

app/assets/stylesheets/application.tailwind.css

app/controllers/assignments_controller.rb

app/models/assignment.rb

app/subscribers/notifications_subscriber.rb

app/views/assignments/_user_add.html.erb

app/views/conferences/show.html.erb

app/views/sessions/_assignment_form.html.erb

app/views/sessions/_session.html.erb

db/migrate/20240526121600_add_telegram_username_to_user.rb

db/schema.rb

db/seeds.rb