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-named-as-default.md

@@ -0,0 +1,53 @@
+# import/no-named-as-default
+
+⚠️ This rule _warns_ in the following configs: ☑️ `recommended`, 🚸 `warnings`.
+
+<!-- end auto-generated rule header -->
+
+Reports use of an exported name as the locally imported name of a default export.
+
+Rationale: using an exported name as the name of the default export is likely...
+
+ - _misleading_: others familiar with `foo.js` probably expect the name to be `foo`
+ - _a mistake_: only needed to import `bar` and forgot the brackets (the case that is prompting this)
+
+## Rule Details
+
+Given:
+
+```js
+// foo.js
+export default 'foo';
+export const bar = 'baz';
+```
+
+...this would be valid:
+
+```js
+import foo from './foo.js';
+```
+
+...and this would be reported:
+
+```js
+// message: Using exported name 'bar' as identifier for default export.
+import bar from './foo.js';
+```
+
+For post-ES2015 `export` extensions, this also prevents exporting the default from a referenced module as a name within that module, for the same reasons:
+
+```js
+// valid:
+export foo from './foo.js';
+
+// message: Using exported name 'bar' as identifier for default export.
+export bar from './foo.js';
+```
+
+## Further Reading
+
+ - ECMAScript Proposal: [export ns from]
+ - ECMAScript Proposal: [export default from]
+
+[export ns from]: https://github.com/leebyron/ecmascript-export-ns-from
+[export default from]: https://github.com/leebyron/ecmascript-export-default-from