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/date-fns/endOfToday/index.js

@@ -0,0 +1,31 @@
+"use strict";
+
+var _interopRequireDefault = require("@babel/runtime/helpers/interopRequireDefault").default;
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.default = endOfToday;
+var _index = _interopRequireDefault(require("../endOfDay/index.js"));
+/**
+ * @name endOfToday
+ * @category Day Helpers
+ * @summary Return the end of today.
+ * @pure false
+ *
+ * @description
+ * Return the end of today.
+ *
+ * > ⚠️ Please note that this function is not present in the FP submodule as
+ * > it uses `Date.now()` internally hence impure and can't be safely curried.
+ *
+ * @returns {Date} the end of today
+ *
+ * @example
+ * // If today is 6 October 2014:
+ * const result = endOfToday()
+ * //=> Mon Oct 6 2014 23:59:59.999
+ */
+function endOfToday() {
+  return (0, _index.default)(Date.now());
+}
+module.exports = exports.default;