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/render/utils/flat-tree.mjs

@@ -0,0 +1,24 @@
+import { addUniqueItem, removeItem } from '../../utils/array.mjs';
+import { compareByDepth } from './compare-by-depth.mjs';
+
+class FlatTree {
+    constructor() {
+        this.children = [];
+        this.isDirty = false;
+    }
+    add(child) {
+        addUniqueItem(this.children, child);
+        this.isDirty = true;
+    }
+    remove(child) {
+        removeItem(this.children, child);
+        this.isDirty = true;
+    }
+    forEach(callback) {
+        this.isDirty && this.children.sort(compareByDepth);
+        this.isDirty = false;
+        this.children.forEach(callback);
+    }
+}
+
+export { FlatTree };