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/eslint-plugin-import/docs/rules/export.md

@@ -0,0 +1,37 @@
+# import/export
+
+💼 This rule is enabled in the following configs: ❗ `errors`, ☑️ `recommended`.
+
+<!-- end auto-generated rule header -->
+
+Reports funny business with exports, like repeated exports of names or defaults.
+
+## Rule Details
+
+```js
+export default class MyClass { /*...*/ } // Multiple default exports.
+
+function makeClass() { return new MyClass(...arguments) }
+
+export default makeClass // Multiple default exports.
+```
+
+or
+
+```js
+export const foo = function () { /*...*/ } // Multiple exports of name 'foo'.
+
+function bar() { /*...*/ }
+export { bar as foo } // Multiple exports of name 'foo'.
+```
+
+In the case of named/default re-export, all `n` re-exports will be reported,
+as at least `n-1` of them are clearly mistakes, but it is not clear which one
+(if any) is intended. Could be the result of copy/paste, code duplication with
+intent to rename, etc.
+
+## Further Reading
+
+ - Lee Byron's [ES7] export proposal
+
+[ES7]: https://github.com/leebyron/ecmascript-more-export-from