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/get-uri/dist/notmodified.js

@@ -0,0 +1,17 @@
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+/**
+ * Error subclass to use when the source has not been modified.
+ *
+ * @param {String} message optional "message" property to set
+ * @api protected
+ */
+class NotModifiedError extends Error {
+    constructor(message) {
+        super(message ||
+            'Source has not been modified since the provied "cache", re-use previous results');
+        this.code = 'ENOTMODIFIED';
+    }
+}
+exports.default = NotModifiedError;
+//# sourceMappingURL=notmodified.js.map