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/lodash/_isFlattenable.js

@@ -0,0 +1,20 @@
+var Symbol = require('./_Symbol'),
+    isArguments = require('./isArguments'),
+    isArray = require('./isArray');
+
+/** Built-in value references. */
+var spreadableSymbol = Symbol ? Symbol.isConcatSpreadable : undefined;
+
+/**
+ * Checks if `value` is a flattenable `arguments` object or array.
+ *
+ * @private
+ * @param {*} value The value to check.
+ * @returns {boolean} Returns `true` if `value` is flattenable, else `false`.
+ */
+function isFlattenable(value) {
+  return isArray(value) || isArguments(value) ||
+    !!(spreadableSymbol && value && value[spreadableSymbol]);
+}
+
+module.exports = isFlattenable;