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/http-link-header/README.md

@@ -0,0 +1,174 @@
+# HTTP Link Header
+[![npm](https://img.shields.io/npm/v/http-link-header.svg?style=flat-square)](https://npmjs.com/http-link-header)
+[![npm license](https://img.shields.io/npm/l/http-link-header.svg?style=flat-square)](https://npmjs.com/http-link-header)
+[![npm downloads](https://img.shields.io/npm/dm/http-link-header.svg?style=flat-square)](https://npmjs.com/http-link-header)
+
+Parse & format HTTP link headers according to [RFC 8288]
+
+[RFC 8288]: https://tools.ietf.org/html/rfc8288
+
+## Install via [npm](https://npmjs.com)
+
+```sh
+$ npm install --save http-link-header
+```
+
+## Deviations from the RFC
+
+### Link Target
+
+While [RFC 8288, Section 3.1](https://tools.ietf.org/html/rfc8288#section-3.1) states that relative URI-References
+MUST be resolved by the parsers – this library DOES NOT.
+This is due to the parser not having an input for the absolute or canonical URI of the related document.
+Currently there are no plans to add this, and it is left to the user whether or not to resolve relative URIs.
+
+## Usage
+
+```js
+var LinkHeader = require( 'http-link-header' )
+```
+
+### Parsing a HTTP link header
+
+```js
+var link = LinkHeader.parse(
+  '<example.com>; rel="example"; title="Example Website", ' +
+  '<example-01.com>; rel="alternate"; title="Alternate Example Domain"'
+)
+
+> Link {
+  refs: [
+    { uri: 'example.com', rel: 'example', title: 'Example Website' },
+    { uri: 'example-01.com', rel: 'alternate', title: 'Alternate Example Domain' },
+  ]
+}
+```
+
+### Checking whether it has a reference with a given attribute & value
+
+```js
+link.has( 'rel', 'alternate' )
+> true
+```
+
+### Retrieving a reference with a given attribute & value
+
+```js
+link.get( 'rel', 'alternate' )
+> [
+  { uri: 'example-01.com', rel: 'alternate', title: 'Alternate Example Domain' }
+]
+```
+```js
+// Shorthand for `rel` attributes
+link.rel( 'alternate' )
+> [
+  { uri: 'example-01.com', rel: 'alternate', title: 'Alternate Example Domain' }
+]
+```
+
+### Setting references
+
+```js
+link.set({ uri: 'https://example.com/next', rel: 'next' })
+> Link {
+  refs: [
+    { uri: 'example.com', rel: 'example', title: 'Example Website' },
+    { uri: 'example-01.com', rel: 'alternate', title: 'Alternate Example Domain' },
+    { rel: 'next', uri: 'https://example.com/next' }
+  ]
+}
+```
+
+### Setting a unique reference
+
+```js
+link.setUnique({
+  uri: 'https://example.com/image.png',
+  rel: 'preload',
+  as: 'image',
+  type: 'image/png'
+})
+> Link {
+  refs: [
+    { uri: 'https://example.com/image.png', rel: 'preload', as: 'image', type: 'image/png' }
+  ]
+}
+
+link.setUnique({
+  uri: 'https://example.com/image.png',
+  rel: 'preload',
+  as: 'image',
+  type: 'image/png'
+})
+> Link {
+  refs: [
+    { uri: 'https://example.com/image.png', rel: 'preload', as: 'image', type: 'image/png' }
+  ]
+}
+```
+
+### Parsing multiple headers
+
+```js
+var link = new LinkHeader()
+
+link.parse( '<example.com>; rel="example"; title="Example Website"' )
+> Link {
+  refs: [
+    { uri: 'example.com', rel: 'example', title: 'Example Website' },
+  ]
+}
+
+link.parse( '<example-01.com>; rel="alternate"; title="Alternate Example Domain"' )
+> Link {
+  refs: [
+    { uri: 'example.com', rel: 'example', title: 'Example Website' },
+    { uri: 'example-01.com', rel: 'alternate', title: 'Alternate Example Domain' },
+  ]
+}
+
+link.parse( '<example-02.com>; rel="alternate"; title="Second Alternate Example Domain"' )
+> Link {
+  refs: [
+    { uri: 'example.com', rel: 'example', title: 'Example Website' },
+    { uri: 'example-01.com', rel: 'alternate', title: 'Alternate Example Domain' },
+    { uri: 'example-02.com', rel: 'alternate', title: 'Second Alternate Example Domain' },
+  ]
+}
+```
+
+### Handling extended attributes
+
+```js
+link.parse( '</extended-attr-example>; rel=start; title*=UTF-8\'en\'%E2%91%A0%E2%93%AB%E2%85%93%E3%8F%A8%E2%99%B3%F0%9D%84%9E%CE%BB' )
+```
+
+```js
+> Link {
+  refs: [
+    { uri: '/extended-attr-example', rel: 'start', 'title*': { language: 'en', encoding: null, value: '①⓫⅓㏨♳𝄞λ' } }
+  ]
+}
+```
+
+### Stringifying to HTTP header format
+
+```js
+link.toString()
+> '<example.com>; rel=example; title="Example Website", <example-01.com>; rel=alternate; title="Alternate Example Domain"'
+```
+
+## Speed
+
+```
+$ npm run benchmark
+```
+
+```
+# http-link-header .parse() ⨉ 1000000
+ok ~1.29 s (1 s + 289696759 ns)
+
+# http-link-header #toString() ⨉ 1000000
+ok ~554 ms (0 s + 553782657 ns)
+```