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/configtest/lib/index.d.ts

@@ -0,0 +1,5 @@
+import { type IWebpackCLI } from "webpack-cli";
+declare class ConfigTestCommand {
+    apply(cli: IWebpackCLI): Promise<void>;
+}
+export default ConfigTestCommand;

node_modules/@webpack-cli/configtest/lib/index.js

@@ -0,0 +1,53 @@
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+const WEBPACK_PACKAGE = process.env.WEBPACK_PACKAGE || "webpack";
+class ConfigTestCommand {
+    async apply(cli) {
+        await cli.makeCommand({
+            name: "configtest [config-path]",
+            alias: "t",
+            description: "Validate a webpack configuration.",
+            pkg: "@webpack-cli/configtest",
+            dependencies: [WEBPACK_PACKAGE],
+        }, [], async (configPath) => {
+            cli.webpack = await cli.loadWebpack();
+            const config = await cli.loadConfig(configPath ? { config: [configPath] } : {});
+            const configPaths = new Set();
+            if (Array.isArray(config.options)) {
+                config.options.forEach((options) => {
+                    const loadedConfigPaths = config.path.get(options);
+                    if (loadedConfigPaths) {
+                        loadedConfigPaths.forEach((path) => configPaths.add(path));
+                    }
+                });
+            }
+            else {
+                if (config.path.get(config.options)) {
+                    const loadedConfigPaths = config.path.get(config.options);
+                    if (loadedConfigPaths) {
+                        loadedConfigPaths.forEach((path) => configPaths.add(path));
+                    }
+                }
+            }
+            if (configPaths.size === 0) {
+                cli.logger.error("No configuration found.");
+                process.exit(2);
+            }
+            cli.logger.info(`Validate '${Array.from(configPaths).join(" ,")}'.`);
+            try {
+                cli.webpack.validate(config.options);
+            }
+            catch (error) {
+                if (cli.isValidationError(error)) {
+                    cli.logger.error(error.message);
+                }
+                else {
+                    cli.logger.error(error);
+                }
+                process.exit(2);
+            }
+            cli.logger.success("There are no validation errors in the given webpack configuration.");
+        });
+    }
+}
+exports.default = ConfigTestCommand;