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/group-exports.md

@@ -0,0 +1,118 @@
+# import/group-exports
+
+<!-- end auto-generated rule header -->
+
+Reports when named exports are not grouped together in a single `export` declaration or when multiple assignments to CommonJS `module.exports` or `exports` object are present in a single file.
+
+**Rationale:** An `export` declaration or `module.exports` assignment can appear anywhere in the code. By requiring a single export declaration all your exports will remain at one place, making it easier to see what exports a module provides.
+
+## Rule Details
+
+This rule warns whenever a single file contains multiple named export declarations or multiple assignments to `module.exports` (or `exports`).
+
+### Valid
+
+```js
+// A single named export declaration -> ok
+export const valid = true
+```
+
+```js
+const first = true
+const second = true
+
+// A single named export declaration -> ok
+export {
+  first,
+  second,
+}
+```
+
+```js
+// Aggregating exports -> ok
+export { default as module1 } from 'module-1'
+export { default as module2 } from 'module-2'
+```
+
+```js
+// A single exports assignment -> ok
+module.exports = {
+  first: true,
+  second: true
+}
+```
+
+```js
+const first = true
+const second = true
+
+// A single exports assignment -> ok
+module.exports = {
+  first,
+  second,
+}
+```
+
+```js
+function test() {}
+test.property = true
+test.another = true
+
+// A single exports assignment -> ok
+module.exports = test
+```
+
+```ts
+const first = true;
+type firstType = boolean
+
+// A single named export declaration (type exports handled separately) -> ok
+export {first}
+export type {firstType}
+```
+
+### Invalid
+
+```js
+// Multiple named export statements -> not ok!
+export const first = true
+export const second = true
+```
+
+```js
+// Aggregating exports from the same module -> not ok!
+export { module1 } from 'module-1'
+export { module2 } from 'module-1'
+```
+
+```js
+// Multiple exports assignments -> not ok!
+exports.first = true
+exports.second = true
+```
+
+```js
+// Multiple exports assignments -> not ok!
+module.exports = {}
+module.exports.first = true
+```
+
+```js
+// Multiple exports assignments -> not ok!
+module.exports = () => {}
+module.exports.first = true
+module.exports.second = true
+```
+
+```ts
+type firstType = boolean
+type secondType = any
+
+// Multiple named type export statements -> not ok!
+export type {firstType}
+export type {secondType}
+```
+
+## When Not To Use It
+
+If you do not mind having your exports spread across the file, you can safely turn this rule off.