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/valtio/ts3.4/utils/proxyWithHistory.d.ts

@@ -0,0 +1,40 @@
+import { INTERNAL_Snapshot } from '../vanilla';
+/**
+ * proxyWithHistory
+ *
+ * This creates a new proxy with history support.
+ * It includes following properties:
+ * - value: any value (does not have to be an object)
+ * - history: an array holding the history of snapshots
+ * - historyIndex: the history index to the current snapshot
+ * - canUndo: a function to return true if undo is available
+ * - undo: a function to go back history
+ * - canRedo: a function to return true if redo is available
+ * - redo: a function to go forward history
+ * - saveHistory: a function to save history
+ *
+ * [Notes]
+ * Suspense/promise is not supported.
+ *
+ * @example
+ * import { proxyWithHistory } from 'valtio/utils'
+ * const state = proxyWithHistory({
+ *   count: 1,
+ * })
+ */
+export declare function proxyWithHistory<V>(initialValue: V, skipSubscribe?: boolean): {
+    value: V;
+    history: {
+        wip: INTERNAL_Snapshot<V> | undefined;
+        snapshots: INTERNAL_Snapshot<V>[];
+        index: number;
+    } & {
+        $$valtioRef: true;
+    };
+    canUndo: () => boolean;
+    undo: () => void;
+    canRedo: () => boolean;
+    redo: () => void;
+    saveHistory: () => void;
+    subscribe: () => () => void;
+};