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/object-inspect/test-core-js.js

@@ -0,0 +1,26 @@
+'use strict';
+
+require('core-js');
+
+var inspect = require('./');
+var test = require('tape');
+
+test('Maps', function (t) {
+    t.equal(inspect(new Map([[1, 2]])), 'Map (1) {1 => 2}');
+    t.end();
+});
+
+test('WeakMaps', function (t) {
+    t.equal(inspect(new WeakMap([[{}, 2]])), 'WeakMap { ? }');
+    t.end();
+});
+
+test('Sets', function (t) {
+    t.equal(inspect(new Set([[1, 2]])), 'Set (1) {[ 1, 2 ]}');
+    t.end();
+});
+
+test('WeakSets', function (t) {
+    t.equal(inspect(new WeakSet([[1, 2]])), 'WeakSet { ? }');
+    t.end();
+});