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/es-abstract/2022/WordCharacters.js

@@ -0,0 +1,46 @@
+'use strict';
+
+var $TypeError = require('es-errors/type');
+
+var callBound = require('call-bound');
+var $indexOf = callBound('String.prototype.indexOf');
+
+var Canonicalize = require('./Canonicalize');
+
+var caseFolding = require('../helpers/caseFolding.json');
+var forEach = require('../helpers/forEach');
+var OwnPropertyKeys = require('own-keys');
+
+var A = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_'; // step 1
+
+// https://262.ecma-international.org/8.0/#sec-runtime-semantics-wordcharacters-abstract-operation
+
+module.exports = function WordCharacters(IgnoreCase, Unicode) {
+	if (typeof IgnoreCase !== 'boolean' || typeof Unicode !== 'boolean') {
+		throw new $TypeError('Assertion failed: `IgnoreCase` and `Unicode` must be booleans');
+	}
+
+	var U = '';
+	forEach(OwnPropertyKeys(caseFolding.C), function (c) {
+		if (
+			$indexOf(A, c) === -1 // c not in A
+			&& $indexOf(A, Canonicalize(c, IgnoreCase, Unicode)) > -1 // canonicalized c IS in A
+		) {
+			U += caseFolding.C[c]; // step 3
+		}
+	});
+	forEach(OwnPropertyKeys(caseFolding.S), function (c) {
+		if (
+			$indexOf(A, c) === -1 // c not in A
+			&& $indexOf(A, Canonicalize(c, IgnoreCase, Unicode)) > -1 // canonicalized c IS in A
+		) {
+			U += caseFolding.S[c]; // step 3
+		}
+	});
+
+	if ((!Unicode || !IgnoreCase) && U.length > 0) {
+		throw new $TypeError('Assertion failed: `U` must be empty when `IgnoreCase` and `Unicode` are not both true'); // step 4
+	}
+
+	return A + U; // step 5, 6
+};