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/build-module/utils/style-mixins.js

@@ -0,0 +1,10 @@
+export { boxSizingReset } from './box-sizing';
+export { rgba } from './colors';
+export { reduceMotion } from './reduce-motion';
+export { rtl } from './rtl';
+export { font } from './font';
+export { breakpoint } from './breakpoint';
+export { default as CONFIG } from './config-values';
+export { COLORS } from './colors-values';
+export { baseLabelTypography } from './base-label';
+//# sourceMappingURL=style-mixins.js.map