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/@emotion/react/src/jsx-dev-runtime.ts

@@ -0,0 +1,37 @@
+import * as ReactJSXRuntimeDev from 'react/jsx-dev-runtime'
+import Emotion, { createEmotionProps } from './emotion-element'
+import { hasOwn } from './utils'
+import { Interpolation } from '@emotion/serialize'
+import { Theme } from './theming'
+export type { EmotionJSX as JSX } from './jsx-namespace'
+
+export const Fragment = ReactJSXRuntimeDev.Fragment
+
+export const jsxDEV: typeof ReactJSXRuntimeDev.jsxDEV = (
+  type,
+  props,
+  key,
+  isStaticChildren,
+  source,
+  self
+) => {
+  if (!hasOwn.call(props, 'css')) {
+    return ReactJSXRuntimeDev.jsxDEV(
+      type,
+      props,
+      key,
+      isStaticChildren,
+      source,
+      self
+    )
+  }
+
+  return ReactJSXRuntimeDev.jsxDEV(
+    Emotion,
+    createEmotionProps(type, props as { css: Interpolation<Theme> }),
+    key,
+    isStaticChildren,
+    source,
+    self
+  )
+}