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/intersection.js

@@ -0,0 +1,30 @@
+var arrayMap = require('./_arrayMap'),
+    baseIntersection = require('./_baseIntersection'),
+    baseRest = require('./_baseRest'),
+    castArrayLikeObject = require('./_castArrayLikeObject');
+
+/**
+ * Creates an array of unique values that are included in all given arrays
+ * using [`SameValueZero`](http://ecma-international.org/ecma-262/7.0/#sec-samevaluezero)
+ * for equality comparisons. The order and references of result values are
+ * determined by the first array.
+ *
+ * @static
+ * @memberOf _
+ * @since 0.1.0
+ * @category Array
+ * @param {...Array} [arrays] The arrays to inspect.
+ * @returns {Array} Returns the new array of intersecting values.
+ * @example
+ *
+ * _.intersection([2, 1], [2, 3]);
+ * // => [2]
+ */
+var intersection = baseRest(function(arrays) {
+  var mapped = arrayMap(arrays, castArrayLikeObject);
+  return (mapped.length && mapped[0] === arrays[0])
+    ? baseIntersection(mapped)
+    : [];
+});
+
+module.exports = intersection;