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/eslint-plugin-jsx-a11y/lib/util/isHiddenFromScreenReader.js

@@ -0,0 +1,26 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports["default"] = void 0;
+var _jsxAstUtils = require("jsx-ast-utils");
+/**
+ * Returns boolean indicating that the aria-hidden prop
+ * is present or the value is true. Will also return true if
+ * there is an input with type='hidden'.
+ *
+ * <div aria-hidden /> is equivalent to the DOM as <div aria-hidden=true />.
+ */
+var isHiddenFromScreenReader = function isHiddenFromScreenReader(type, attributes) {
+  if (type.toUpperCase() === 'INPUT') {
+    var hidden = (0, _jsxAstUtils.getLiteralPropValue)((0, _jsxAstUtils.getProp)(attributes, 'type'));
+    if (hidden && hidden.toUpperCase() === 'HIDDEN') {
+      return true;
+    }
+  }
+  var ariaHidden = (0, _jsxAstUtils.getPropValue)((0, _jsxAstUtils.getProp)(attributes, 'aria-hidden'));
+  return ariaHidden === true;
+};
+var _default = exports["default"] = isHiddenFromScreenReader;
+module.exports = exports.default;