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/postcss/lib/root.d.ts

@@ -0,0 +1,86 @@
+import Container, { ContainerProps } from './container.js'
+import Document from './document.js'
+import { ProcessOptions } from './postcss.js'
+import Result from './result.js'
+
+declare namespace Root {
+  export interface RootRaws extends Record<string, any> {
+    /**
+     * The space symbols after the last child to the end of file.
+     */
+    after?: string
+
+    /**
+     * Non-CSS code after `Root`, when `Root` is inside `Document`.
+     *
+     * **Experimental:** some aspects of this node could change within minor
+     * or patch version releases.
+     */
+    codeAfter?: string
+
+    /**
+     * Non-CSS code before `Root`, when `Root` is inside `Document`.
+     *
+     * **Experimental:** some aspects of this node could change within minor
+     * or patch version releases.
+     */
+    codeBefore?: string
+
+    /**
+     * Is the last child has an (optional) semicolon.
+     */
+    semicolon?: boolean
+  }
+
+  export interface RootProps extends ContainerProps {
+    /**
+     * Information used to generate byte-to-byte equal node string
+     * as it was in the origin input.
+     * */
+    raws?: RootRaws
+  }
+
+  export { Root_ as default }
+}
+
+/**
+ * Represents a CSS file and contains all its parsed nodes.
+ *
+ * ```js
+ * const root = postcss.parse('a{color:black} b{z-index:2}')
+ * root.type         //=> 'root'
+ * root.nodes.length //=> 2
+ * ```
+ */
+declare class Root_ extends Container {
+  nodes: NonNullable<Container['nodes']>
+  parent: Document | undefined
+  raws: Root.RootRaws
+  type: 'root'
+
+  constructor(defaults?: Root.RootProps)
+
+  assign(overrides: object | Root.RootProps): this
+  clone(overrides?: Partial<Root.RootProps>): this
+  cloneAfter(overrides?: Partial<Root.RootProps>): this
+  cloneBefore(overrides?: Partial<Root.RootProps>): this
+
+  /**
+   * Returns a `Result` instance representing the root’s CSS.
+   *
+   * ```js
+   * const root1 = postcss.parse(css1, { from: 'a.css' })
+   * const root2 = postcss.parse(css2, { from: 'b.css' })
+   * root1.append(root2)
+   * const result = root1.toResult({ to: 'all.css', map: true })
+   * ```
+   *
+   * @param options Options.
+   * @return Result with current root’s CSS.
+   */
+  toResult(options?: ProcessOptions): Result
+}
+
+declare class Root extends Root_ {}
+
+export = Root