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/isFinite.js

@@ -0,0 +1,12 @@
+'use strict';
+
+var $isNaN = require('./isNaN');
+
+/** @type {import('./isFinite')} */
+module.exports = function isFinite(x) {
+	return (typeof x === 'number' || typeof x === 'bigint')
+        && !$isNaN(x)
+        && x !== Infinity
+        && x !== -Infinity;
+};
+