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/@wordpress/components/src/combobox-control/README.md

@@ -0,0 +1,117 @@
+# ComboboxControl
+
+`ComboboxControl` is an enhanced version of a [`SelectControl`](/packages/components/src/select-control/README.md), with the addition of being able to search for options using a search input.
+
+## Design guidelines
+
+These are the same as [the ones for `SelectControl`s](/packages/components/src/select-control/README.md#design-guidelines), but this component is better suited for when there are too many items to scroll through or load at once so you need to filter them based on user input.
+
+## Development guidelines
+
+### Usage
+
+```jsx
+import { useState } from 'react';
+import { ComboboxControl } from '@wordpress/components';
+
+const options = [
+	{
+		value: 'small',
+		label: 'Small',
+	},
+	{
+		value: 'normal',
+		label: 'Normal',
+	},
+	{
+		value: 'large',
+		label: 'Large',
+	},
+];
+
+function MyComboboxControl() {
+	const [ fontSize, setFontSize ] = useState();
+	const [ filteredOptions, setFilteredOptions ] = useState( options );
+	return (
+		<ComboboxControl
+			label="Font Size"
+			value={ fontSize }
+			onChange={ setFontSize }
+			options={ filteredOptions }
+			onFilterValueChange={ ( inputValue ) =>
+				setFilteredOptions(
+					options.filter( ( option ) =>
+						option.value === inputValue
+					)
+				)
+			}
+		/>
+	);
+}
+```
+
+### Props
+
+#### label
+
+The label for the control.
+
+-   Type: `String`
+-   Required: Yes
+
+#### hideLabelFromVision
+
+If true, the label will only be visible to screen readers.
+
+-   Type: `Boolean`
+-   Required: No
+
+#### help
+
+If this property is added, a help text will be generated using help property as the content.
+
+-   Type: `String`
+-   Required: No
+
+#### options
+
+The options that can be chosen from.
+
+-   Type: `Array<{ value: string, label: string }>`
+-   Required: Yes
+
+#### onFilterValueChange
+
+Function called when the control's search input value changes. The argument contains the next input value.
+
+-   Type: `( value: string ) => void`
+-   Required: No
+
+#### onChange
+
+Function called with the selected value changes.
+
+-   Type: `( value: string | null | undefined ) => void`
+-   Required: No
+
+#### value
+
+The current value of the control.
+
+-   Type: `string | null`
+-   Required: No
+
+#### __experimentalRenderItem
+
+Custom renderer invoked for each option in the suggestion list. The render prop receives as its argument an object containing, under the `item` key, the single option's data (directly from the array of data passed to the `options` prop).
+
+-   Type: `( args: { item: object } ) => ReactNode`
+-   Required: No
+
+## Related components
+
+-   Like this component, but without a search input, the `CustomSelectControl` component.
+
+-   To select one option from a set, when you want to show all the available options at once, use the `Radio` component.
+-   To select one or more items from a set, use the `CheckboxControl` component.
+-   To toggle a single setting on or off, use the `ToggleControl` component.