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/resolve-bin/examples/open-cli.js

@@ -0,0 +1,27 @@
+'use strict';
+
+var resolveBin = require('../');
+
+// package.json:
+// "bin": {
+//   "open-cli": "cli.js"
+// },
+
+resolveBin('open-cli', function (err, bin) {
+  if (err) return console.error(err);
+  console.log(bin);
+});
+
+// => [..]/resolve-bin/node_modules/open-cli/cli.js
+
+
+resolveBin('open-cli', { executable: 'open-cli' }, function (err, bin) {
+  if (err) return console.error(err);
+  console.log(bin);
+});
+
+// => [..]/resolve-bin/node_modules/open-cli/cli.js
+
+console.log(resolveBin.sync('open-cli'));
+// => [..]/resolve-bin/node_modules/open-cli/cli.js
+