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/@wordpress/icons/build-module/library/file.js

@@ -0,0 +1,15 @@
+import { createElement } from "react";
+/**
+ * WordPress dependencies
+ */
+import { Path, SVG } from '@wordpress/primitives';
+const file = createElement(SVG, {
+  viewBox: "0 0 24 24",
+  xmlns: "http://www.w3.org/2000/svg"
+}, createElement(Path, {
+  fillRule: "evenodd",
+  clipRule: "evenodd",
+  d: "M12.848 8a1 1 0 0 1-.914-.594l-.723-1.63a.5.5 0 0 0-.447-.276H5a.5.5 0 0 0-.5.5v11.5a.5.5 0 0 0 .5.5h14a.5.5 0 0 0 .5-.5v-9A.5.5 0 0 0 19 8h-6.152Zm.612-1.5a.5.5 0 0 1-.462-.31l-.445-1.084A2 2 0 0 0 10.763 4H5a2 2 0 0 0-2 2v11.5a2 2 0 0 0 2 2h14a2 2 0 0 0 2-2v-9a2 2 0 0 0-2-2h-5.54Z"
+}));
+export default file;
+//# sourceMappingURL=file.js.map