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/@sinonjs/commons/README.md

@@ -0,0 +1,16 @@
+# commons
+
+[![CircleCI](https://circleci.com/gh/sinonjs/commons.svg?style=svg)](https://circleci.com/gh/sinonjs/commons)
+[![codecov](https://codecov.io/gh/sinonjs/commons/branch/master/graph/badge.svg)](https://codecov.io/gh/sinonjs/commons)
+<a href="CODE_OF_CONDUCT.md"><img src="https://img.shields.io/badge/Contributor%20Covenant-v2.0%20adopted-ff69b4.svg" alt="Contributor Covenant" /></a>
+
+Simple functions shared among the sinon end user libraries
+
+## Rules
+
+-   Follows the [Sinon.JS compatibility](https://github.com/sinonjs/sinon/blob/master/CONTRIBUTING.md#compatibility)
+-   100% test coverage
+-   Code formatted using [Prettier](https://prettier.io)
+-   No side effects welcome! (only pure functions)
+-   No platform specific functions
+-   One export per file (any bundler can do tree shaking)