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/axios/lib/helpers/readBlob.js

@@ -0,0 +1,15 @@
+const { asyncIterator } = Symbol;
+
+const readBlob = async function* (blob) {
+  if (blob.stream) {
+    yield* blob.stream();
+  } else if (blob.arrayBuffer) {
+    yield await blob.arrayBuffer();
+  } else if (blob[asyncIterator]) {
+    yield* blob[asyncIterator]();
+  } else {
+    yield blob;
+  }
+};
+
+export default readBlob;