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/framer-motion/dist/es/easing/back.mjs

@@ -0,0 +1,9 @@
+import { cubicBezier } from './cubic-bezier.mjs';
+import { mirrorEasing } from './modifiers/mirror.mjs';
+import { reverseEasing } from './modifiers/reverse.mjs';
+
+const backOut = cubicBezier(0.33, 1.53, 0.69, 0.99);
+const backIn = reverseEasing(backOut);
+const backInOut = mirrorEasing(backIn);
+
+export { backIn, backInOut, backOut };