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/tree-kill/index.d.ts

@@ -0,0 +1,13 @@
+/**
+ * Kills process identified by `pid` and all its children
+ *
+ * @param pid
+ * @param signal 'SIGTERM' by default
+ * @param callback
+ */
+declare function treeKill(pid: number, callback?: (error?: Error) => void): void;
+declare function treeKill(pid: number, signal?: string | number, callback?: (error?: Error) => void): void;
+
+declare namespace treeKill {}
+
+export = treeKill;