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/no-relative-parent-imports.md

@@ -0,0 +1,123 @@
+# import/no-relative-parent-imports
+
+<!-- end auto-generated rule header -->
+
+Use this rule to prevent imports to folders in relative parent paths.
+
+This rule is useful for enforcing tree-like folder structures instead of complex graph-like folder structures. While this restriction might be a departure from Node's default resolution style, it can lead large, complex codebases to be easier to maintain. If you've ever had debates over "where to put files" this rule is for you.
+
+To fix violations of this rule there are three general strategies. Given this example:
+
+```pt
+numbers
+└── three.js
+add.js
+```
+
+```js
+// ./add.js
+export default function (numbers) {
+  return numbers.reduce((sum, n) => sum + n, 0);
+}
+
+// ./numbers/three.js
+import add from '../add'; // violates import/no-relative-parent-imports
+
+export default function three() {
+  return add([1, 2]);
+}
+```
+
+You can,
+
+1. Move the file to be in a sibling folder (or higher) of the dependency.
+
+   `three.js` could be be in the same folder as `add.js`:
+
+   ```pt
+   three.js
+   add.js
+   ```
+
+   or since `add` doesn't have any imports, it could be in it's own directory (namespace):
+
+   ```pt
+   math
+   └── add.js
+   three.js
+   ```
+
+2. Pass the dependency as an argument at runtime (dependency injection)
+
+   ```js
+   // three.js
+   export default function three(add) {
+     return add([1, 2]);
+   }
+
+   // somewhere else when you use `three.js`:
+   import add from './add';
+   import three from './numbers/three';
+   console.log(three(add));
+   ```
+
+3. Make the dependency a package so it's globally available to all files in your project:
+
+   ```js
+   import add from 'add'; // from https://www.npmjs.com/package/add
+   export default function three() {
+     return add([1,2]);
+   }
+   ```
+
+These are (respectively) static, dynamic & global solutions to graph-like dependency resolution.
+
+## Examples
+
+Given the following folder structure:
+
+```pt
+my-project
+├── lib
+│   ├── a.js
+│   └── b.js
+└── main.js
+```
+
+And the .eslintrc file:
+
+```json
+{
+  ...
+  "rules": {
+    "import/no-relative-parent-imports": "error"
+  }
+}
+```
+
+The following patterns are considered problems:
+
+```js
+/**
+ *  in my-project/lib/a.js
+ */
+
+import bar from '../main'; // Import parent file using a relative path
+```
+
+The following patterns are NOT considered problems:
+
+```js
+/**
+ *  in my-project/main.js
+ */
+
+import foo from 'foo'; // Import package using module path
+import a from './lib/a'; // Import child file using relative path
+
+/**
+ *  in my-project/lib/a.js
+ */
+
+import b from './b'; // Import sibling file using relative path
+```