fix: prevent asset conflicts between React and Grid.js versions

Add coexistence checks to all enqueue methods to prevent loading
both React and Grid.js assets simultaneously.

Changes:
- ReactAdmin.php: Only enqueue React assets when ?react=1
- Init.php: Skip Grid.js when React active on admin pages
- Form.php, Coupon.php, Access.php: Restore classic assets when ?react=0
- Customer.php, Product.php, License.php: Add coexistence checks

Now the toggle between Classic and React versions works correctly.

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

node_modules/webpack-sources/lib/helpers/getGeneratedSourceInfo.js

@@ -0,0 +1,44 @@
+/*
+	MIT License http://www.opensource.org/licenses/mit-license.php
+	Author Tobias Koppers @sokra
+*/
+
+"use strict";
+
+const CHAR_CODE_NEW_LINE = "\n".charCodeAt(0);
+
+/**
+ * @typedef {object} GeneratedSourceInfo
+ * @property {number=} generatedLine generated line
+ * @property {number=} generatedColumn generated column
+ * @property {string=} source source
+ */
+
+/**
+ * @param {string | undefined} source source
+ * @returns {GeneratedSourceInfo} source info
+ */
+const getGeneratedSourceInfo = (source) => {
+	if (source === undefined) {
+		return {};
+	}
+	const lastLineStart = source.lastIndexOf("\n");
+	if (lastLineStart === -1) {
+		return {
+			generatedLine: 1,
+			generatedColumn: source.length,
+			source,
+		};
+	}
+	let generatedLine = 2;
+	for (let i = 0; i < lastLineStart; i++) {
+		if (source.charCodeAt(i) === CHAR_CODE_NEW_LINE) generatedLine++;
+	}
+	return {
+		generatedLine,
+		generatedColumn: source.length - lastLineStart - 1,
+		source,
+	};
+};
+
+module.exports = getGeneratedSourceInfo;