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/core-js/modules/es.uint8-array.to-hex.js

@@ -0,0 +1,36 @@
+'use strict';
+var $ = require('../internals/export');
+var globalThis = require('../internals/global-this');
+var uncurryThis = require('../internals/function-uncurry-this');
+var anUint8Array = require('../internals/an-uint8-array');
+var notDetached = require('../internals/array-buffer-not-detached');
+
+var numberToString = uncurryThis(1.1.toString);
+var join = uncurryThis([].join);
+var $Array = Array;
+
+var Uint8Array = globalThis.Uint8Array;
+
+var INCORRECT_BEHAVIOR_OR_DOESNT_EXISTS = !Uint8Array || !Uint8Array.prototype.toHex || !(function () {
+  try {
+    var target = new Uint8Array([255, 255, 255, 255, 255, 255, 255, 255]);
+    return target.toHex() === 'ffffffffffffffff';
+  } catch (error) {
+    return false;
+  }
+})();
+
+// `Uint8Array.prototype.toHex` method
+// https://tc39.es/ecma262/#sec-uint8array.prototype.tohex
+if (Uint8Array) $({ target: 'Uint8Array', proto: true, forced: INCORRECT_BEHAVIOR_OR_DOESNT_EXISTS }, {
+  toHex: function toHex() {
+    anUint8Array(this);
+    notDetached(this.buffer);
+    var result = $Array(this.length);
+    for (var i = 0, length = this.length; i < length; i++) {
+      var hex = numberToString(this[i], 16);
+      result[i] = hex.length === 1 ? '0' + hex : hex;
+    }
+    return join(result, '');
+  }
+});