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/framer-motion/dist/es/gestures/utils/is-node-or-child.mjs

@@ -0,0 +1,20 @@
+/**
+ * Recursively traverse up the tree to check whether the provided child node
+ * is the parent or a descendant of it.
+ *
+ * @param parent - Element to find
+ * @param child - Element to test against parent
+ */
+const isNodeOrChild = (parent, child) => {
+    if (!child) {
+        return false;
+    }
+    else if (parent === child) {
+        return true;
+    }
+    else {
+        return isNodeOrChild(parent, child.parentElement);
+    }
+};
+
+export { isNodeOrChild };