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/library/code.js

@@ -0,0 +1,20 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.default = void 0;
+var _react = require("react");
+var _primitives = require("@wordpress/primitives");
+/**
+ * WordPress dependencies
+ */
+
+const code = (0, _react.createElement)(_primitives.SVG, {
+  viewBox: "0 0 24 24",
+  xmlns: "http://www.w3.org/2000/svg"
+}, (0, _react.createElement)(_primitives.Path, {
+  d: "M20.8 10.7l-4.3-4.3-1.1 1.1 4.3 4.3c.1.1.1.3 0 .4l-4.3 4.3 1.1 1.1 4.3-4.3c.7-.8.7-1.9 0-2.6zM4.2 11.8l4.3-4.3-1-1-4.3 4.3c-.7.7-.7 1.8 0 2.5l4.3 4.3 1.1-1.1-4.3-4.3c-.2-.1-.2-.3-.1-.4z"
+}));
+var _default = exports.default = code;
+//# sourceMappingURL=code.js.map