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/webpack-cli/bin/cli.js

@@ -0,0 +1,17 @@
+#!/usr/bin/env node
+
+"use strict";
+
+const importLocal = require("import-local");
+const runCLI = require("../lib/bootstrap");
+
+if (!process.env.WEBPACK_CLI_SKIP_IMPORT_LOCAL) {
+  // Prefer the local installation of `webpack-cli`
+  if (importLocal(__filename)) {
+    return;
+  }
+}
+
+process.title = "webpack";
+
+runCLI(process.argv);