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/findMediaOperator.js

@@ -0,0 +1,30 @@
+'use strict';
+
+const styleSearch = require('style-search');
+
+const rangeOperators = ['>=', '<=', '>', '<', '='];
+
+/** @typedef {import('style-search').StyleSearchMatch} StyleSearchMatch */
+
+/**
+ * @template {import('postcss').AtRule} T
+ * @param {T} atRule
+ * @param {(match: StyleSearchMatch, params: string, atRule: T) => void} cb
+ */
+module.exports = function findMediaOperator(atRule, cb) {
+	if (atRule.name.toLowerCase() !== 'media') {
+		return;
+	}
+
+	const params = atRule.raws.params ? atRule.raws.params.raw : atRule.params;
+
+	styleSearch({ source: params, target: rangeOperators }, (match) => {
+		const before = params[match.startIndex - 1];
+
+		if (before === '>' || before === '<') {
+			return;
+		}
+
+		cb(match, params, atRule);
+	});
+};