This commit removes jQuery and the jQuery.tmpl plugin from the frontend,
refactoring all JavaScript code in static/ui.js and relevant HTML files
to use vanilla JavaScript APIs.

Key changes include:
- Replaced jQuery selectors ($) with document.querySelector/querySelectorAll.
- Replaced jQuery DOM manipulation methods with native equivalents (classList,
  style, appendChild, etc.).
- Replaced jQuery event handling (ready, on, keydown) with
  addEventListener.
- Replaced $.getJSON with the fetch API.
- Replaced $.each with Array.prototype.forEach.
- Implemented a custom vanilla JS templating function (`renderTemplate`) to
  replace jquery.tmpl.js functionality, including support for variable
  interpolation, conditionals (if/else), and raw HTML rendering.
- Updated Backbone.js views to handle their own DOM interactions and event
  delegation using vanilla JS, removing the `events` hash and using
  manual event listener attachment in `render` or `attachEvents` methods.
- Removed script tags for jquery and jquery.tmpl from HTML files.
- Replaced inline jQuery calls in HTML onclick attributes with vanilla JS.