Website restoration: Node.js backend, restored design, GitHub sync disabled

- Replaced broken .NET backend with Node.js/Express
- Restored original website design with purple gradient hero
- Updated homepage and shop pages with Bootstrap 5 responsive design
- Disabled GitHub remote sync - all code now stored locally only
- Created backup scripts and documentation
- All changes saved on Ubuntu server at /var/www/SkyArtShop

backend/node_modules/math-intrinsics/isNegativeZero.js

@@ -0,0 +1,6 @@
+'use strict';
+
+/** @type {import('./isNegativeZero')} */
+module.exports = function isNegativeZero(x) {
+	return x === 0 && 1 / x === 1 / -0;
+};