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/_baseFindKey.js

@@ -0,0 +1,23 @@
+/**
+ * The base implementation of methods like `_.findKey` and `_.findLastKey`,
+ * without support for iteratee shorthands, which iterates over `collection`
+ * using `eachFunc`.
+ *
+ * @private
+ * @param {Array|Object} collection The collection to inspect.
+ * @param {Function} predicate The function invoked per iteration.
+ * @param {Function} eachFunc The function to iterate over `collection`.
+ * @returns {*} Returns the found element or its key, else `undefined`.
+ */
+function baseFindKey(collection, predicate, eachFunc) {
+  var result;
+  eachFunc(collection, function(value, key, collection) {
+    if (predicate(value, key, collection)) {
+      result = key;
+      return false;
+    }
+  });
+  return result;
+}
+
+module.exports = baseFindKey;