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/stylelint/lib/rules/declarationBangSpaceChecker.js

@@ -0,0 +1,60 @@
+'use strict';
+
+const declarationValueIndex = require('../utils/declarationValueIndex');
+const report = require('../utils/report');
+const styleSearch = require('style-search');
+
+/** @typedef {import('postcss').Declaration} Declaration */
+
+/** @typedef {(args: { source: string, index: number, err: (message: string) => void }) => void} LocationChecker */
+
+/**
+ * @param {{
+ *   root: import('postcss').Root,
+ *   locationChecker: LocationChecker,
+ *   result: import('stylelint').PostcssResult,
+ *   checkedRuleName: string,
+ *   fix: ((decl: Declaration, index: number) => boolean) | null,
+ * }} opts
+ * @returns {void}
+ */
+module.exports = function declarationBangSpaceChecker(opts) {
+	opts.root.walkDecls((decl) => {
+		const indexOffset = declarationValueIndex(decl);
+		const declString = decl.toString();
+		const valueString = decl.toString().slice(indexOffset);
+
+		if (!valueString.includes('!')) {
+			return;
+		}
+
+		styleSearch({ source: valueString, target: '!' }, (match) => {
+			check(declString, match.startIndex + indexOffset, decl);
+		});
+	});
+
+	/**
+	 * @param {string} source
+	 * @param {number} index
+	 * @param {Declaration} decl
+	 */
+	function check(source, index, decl) {
+		opts.locationChecker({
+			source,
+			index,
+			err: (message) => {
+				if (opts.fix && opts.fix(decl, index)) {
+					return;
+				}
+
+				report({
+					message,
+					node: decl,
+					index,
+					result: opts.result,
+					ruleName: opts.checkedRuleName,
+				});
+			},
+		});
+	}
+};