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/eslint-plugin-playwright/lib/rules/no-conditional-in-test.js

@@ -0,0 +1,32 @@
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+const ast_1 = require("../utils/ast");
+exports.default = {
+    create(context) {
+        function checkConditional(node) {
+            const call = (0, ast_1.findParent)(node, 'CallExpression');
+            if (call && (0, ast_1.isTest)(call)) {
+                context.report({ messageId: 'conditionalInTest', node });
+            }
+        }
+        return {
+            ConditionalExpression: checkConditional,
+            IfStatement: checkConditional,
+            LogicalExpression: checkConditional,
+            SwitchStatement: checkConditional,
+        };
+    },
+    meta: {
+        docs: {
+            category: 'Best Practices',
+            description: 'Disallow conditional logic in tests',
+            recommended: true,
+            url: 'https://github.com/playwright-community/eslint-plugin-playwright/tree/main/docs/rules/no-conditional-in-test.md',
+        },
+        messages: {
+            conditionalInTest: 'Avoid having conditionals in tests',
+        },
+        schema: [],
+        type: 'problem',
+    },
+};