Remove jQuery from Rails App (Vanilla JS)

Task: Strip out legacy jQuery code from a large Ruby on Rails application and replace it with Vanilla JS (ES6) and Fetch API. The current DOM manipulation is causing 3-second freezes on data-heavy tables. No new frontend frameworks needed—just clean up the existing asset pipeline, rewrite the event listeners, and optimize the table rendering. Prioritized list of the 5 worst views is ready for review.