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-dev-middleware/dist/utils/setupOutputFileSystem.js

@@ -0,0 +1,58 @@
+"use strict";
+
+const path = require("path");
+
+const memfs = require("memfs");
+/** @typedef {import("webpack").MultiCompiler} MultiCompiler */
+
+/** @typedef {import("../index.js").IncomingMessage} IncomingMessage */
+
+/** @typedef {import("../index.js").ServerResponse} ServerResponse */
+
+/**
+ * @template {IncomingMessage} Request
+ * @template {ServerResponse} Response
+ * @param {import("../index.js").Context<Request, Response>} context
+ */
+
+
+function setupOutputFileSystem(context) {
+  let outputFileSystem;
+
+  if (context.options.outputFileSystem) {
+    const {
+      outputFileSystem: outputFileSystemFromOptions
+    } = context.options; // Todo remove when we drop webpack@4 support
+
+    if (typeof outputFileSystemFromOptions.join !== "function") {
+      throw new Error("Invalid options: options.outputFileSystem.join() method is expected");
+    } // Todo remove when we drop webpack@4 support
+    // @ts-ignore
+
+
+    if (typeof outputFileSystemFromOptions.mkdirp !== "function") {
+      throw new Error("Invalid options: options.outputFileSystem.mkdirp() method is expected");
+    }
+
+    outputFileSystem = outputFileSystemFromOptions;
+  } else {
+    outputFileSystem = memfs.createFsFromVolume(new memfs.Volume()); // TODO: remove when we drop webpack@4 support
+    // @ts-ignore
+
+    outputFileSystem.join = path.join.bind(path);
+  }
+
+  const compilers =
+  /** @type {MultiCompiler} */
+  context.compiler.compilers || [context.compiler];
+
+  for (const compiler of compilers) {
+    compiler.outputFileSystem = outputFileSystem;
+  } // @ts-ignore
+  // eslint-disable-next-line no-param-reassign
+
+
+  context.outputFileSystem = outputFileSystem;
+}
+
+module.exports = setupOutputFileSystem;