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/lodash/invoke.js

@@ -0,0 +1,24 @@
+var baseInvoke = require('./_baseInvoke'),
+    baseRest = require('./_baseRest');
+
+/**
+ * Invokes the method at `path` of `object`.
+ *
+ * @static
+ * @memberOf _
+ * @since 4.0.0
+ * @category Object
+ * @param {Object} object The object to query.
+ * @param {Array|string} path The path of the method to invoke.
+ * @param {...*} [args] The arguments to invoke the method with.
+ * @returns {*} Returns the result of the invoked method.
+ * @example
+ *
+ * var object = { 'a': [{ 'b': { 'c': [1, 2, 3, 4] } }] };
+ *
+ * _.invoke(object, 'a[0].b.c.slice', 1, 3);
+ * // => [2, 3]
+ */
+var invoke = baseRest(baseInvoke);
+
+module.exports = invoke;