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/internals/string-trim.js

@@ -0,0 +1,31 @@
+'use strict';
+var uncurryThis = require('../internals/function-uncurry-this');
+var requireObjectCoercible = require('../internals/require-object-coercible');
+var toString = require('../internals/to-string');
+var whitespaces = require('../internals/whitespaces');
+
+var replace = uncurryThis(''.replace);
+var ltrim = RegExp('^[' + whitespaces + ']+');
+var rtrim = RegExp('(^|[^' + whitespaces + '])[' + whitespaces + ']+$');
+
+// `String.prototype.{ trim, trimStart, trimEnd, trimLeft, trimRight }` methods implementation
+var createMethod = function (TYPE) {
+  return function ($this) {
+    var string = toString(requireObjectCoercible($this));
+    if (TYPE & 1) string = replace(string, ltrim, '');
+    if (TYPE & 2) string = replace(string, rtrim, '$1');
+    return string;
+  };
+};
+
+module.exports = {
+  // `String.prototype.{ trimLeft, trimStart }` methods
+  // https://tc39.es/ecma262/#sec-string.prototype.trimstart
+  start: createMethod(1),
+  // `String.prototype.{ trimRight, trimEnd }` methods
+  // https://tc39.es/ecma262/#sec-string.prototype.trimend
+  end: createMethod(2),
+  // `String.prototype.trim` method
+  // https://tc39.es/ecma262/#sec-string.prototype.trim
+  trim: createMethod(3)
+};