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/@bcoe/v8-coverage/README.md

@@ -0,0 +1,11 @@
+# V8 Coverage
+
+[![npm](https://img.shields.io/npm/v/@c88/v8-coverage.svg?maxAge=2592000)](https://www.npmjs.com/package/@c88/v8-coverage)
+[![GitHub repository](https://img.shields.io/badge/Github-demurgos%2Fv8--coverage-blue.svg)](https://github.com/demurgos/v8-coverage)
+[![Build status (Travis)](https://img.shields.io/travis/demurgos/v8-coverage/master.svg?maxAge=2592000)](https://travis-ci.org/demurgos/v8-coverage)
+[![Build status (AppVeyor)](https://ci.appveyor.com/api/projects/status/qgcbdffyb9e09d0e?svg=true)](https://ci.appveyor.com/project/demurgos/v8-coverage)
+[![Codecov](https://codecov.io/gh/demurgos/v8-coverage/branch/master/graph/badge.svg)](https://codecov.io/gh/demurgos/v8-coverage)
+
+## License
+
+[MIT License](./LICENSE.md)