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/utils/use-instant-transition.mjs

@@ -0,0 +1,41 @@
+import { useRef, useEffect } from 'react';
+import { useInstantLayoutTransition } from '../projection/use-instant-layout-transition.mjs';
+import { useForceUpdate } from './use-force-update.mjs';
+import { instantAnimationState } from './use-instant-transition-state.mjs';
+import { frame } from '../frameloop/frame.mjs';
+
+function useInstantTransition() {
+    const [forceUpdate, forcedRenderCount] = useForceUpdate();
+    const startInstantLayoutTransition = useInstantLayoutTransition();
+    const unlockOnFrameRef = useRef();
+    useEffect(() => {
+        /**
+         * Unblock after two animation frames, otherwise this will unblock too soon.
+         */
+        frame.postRender(() => frame.postRender(() => {
+            /**
+             * If the callback has been called again after the effect
+             * triggered this 2 frame delay, don't unblock animations. This
+             * prevents the previous effect from unblocking the current
+             * instant transition too soon. This becomes more likely when
+             * used in conjunction with React.startTransition().
+             */
+            if (forcedRenderCount !== unlockOnFrameRef.current)
+                return;
+            instantAnimationState.current = false;
+        }));
+    }, [forcedRenderCount]);
+    return (callback) => {
+        startInstantLayoutTransition(() => {
+            instantAnimationState.current = true;
+            forceUpdate();
+            callback();
+            unlockOnFrameRef.current = forcedRenderCount + 1;
+        });
+    };
+}
+function disableInstantTransitions() {
+    instantAnimationState.current = false;
+}
+
+export { disableInstantTransitions, useInstantTransition };