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/graphemer/lib/GraphemerIterator.d.ts

@@ -0,0 +1,22 @@
+/**
+ * GraphemerIterator
+ *
+ * Takes a string and a "BreakHandler" method during initialisation
+ * and creates an iterable object that returns individual graphemes.
+ *
+ * @param str {string}
+ * @return GraphemerIterator
+ */
+declare class GraphemerIterator implements Iterator<string> {
+    private _index;
+    private _str;
+    private _nextBreak;
+    constructor(str: string, nextBreak: (str: string, index: number) => number);
+    [Symbol.iterator](): this;
+    next(): {
+        value: string;
+        done: boolean;
+    };
+}
+export default GraphemerIterator;
+//# sourceMappingURL=GraphemerIterator.d.ts.map