remove ancient jquery dependency replace with vanilla javascript

[mlinksva]

Fixes #1139

[Copilot]

Pull request overview

This PR removes the ancient jQuery dependency (v1.11.0) and replaces all jQuery usage with vanilla JavaScript. The changes modernize the codebase by using native DOM APIs, the Fetch API, and modern JavaScript features.

Key Changes:

• Complete removal of jQuery library files and dependencies
• Refactoring of DOM selection using querySelector and querySelectorAll
• Event handling migrated from jQuery's .on() to native addEventListener
• AJAX requests replaced with modern Fetch API
• DOM manipulation updated to use native classList and setAttribute methods

Reviewed changes

Copilot reviewed 3 out of 15 changed files in this pull request and generated no comments.

File	Description
bower.json	Removed jQuery dependency from package dependencies
assets/vendor/jquery/*	Removed entire jQuery vendor directory including source, minified, and migration files
assets/js/app.js	Refactored all jQuery code to vanilla JavaScript with proper event handling and DOM manipulation
_includes/footer.html	Removed jQuery script tag from footer template

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.