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/sortedLastIndex.js

@@ -0,0 +1,25 @@
+var baseSortedIndex = require('./_baseSortedIndex');
+
+/**
+ * This method is like `_.sortedIndex` except that it returns the highest
+ * index at which `value` should be inserted into `array` in order to
+ * maintain its sort order.
+ *
+ * @static
+ * @memberOf _
+ * @since 3.0.0
+ * @category Array
+ * @param {Array} array The sorted array to inspect.
+ * @param {*} value The value to evaluate.
+ * @returns {number} Returns the index at which `value` should be inserted
+ *  into `array`.
+ * @example
+ *
+ * _.sortedLastIndex([4, 5, 5, 5, 6], 5);
+ * // => 4
+ */
+function sortedLastIndex(array, value) {
+  return baseSortedIndex(array, value, true);
+}
+
+module.exports = sortedLastIndex;