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/messages/eslintrc-incompat.js

@@ -0,0 +1,98 @@
+"use strict";
+
+/* eslint consistent-return: 0 -- no default case */
+
+const messages = {
+
+    env: `
+A config object is using the "env" key, which is not supported in flat config system.
+
+Flat config uses "languageOptions.globals" to define global variables for your files.
+
+Please see the following page for information on how to convert your config object into the correct format:
+https://eslint.org/docs/latest/use/configure/migration-guide#configuring-language-options
+`,
+
+    extends: `
+A config object is using the "extends" key, which is not supported in flat config system.
+
+Instead of "extends", you can include config objects that you'd like to extend from directly in the flat config array.
+
+Please see the following page for more information:
+https://eslint.org/docs/latest/use/configure/migration-guide#predefined-and-shareable-configs
+`,
+
+    globals: `
+A config object is using the "globals" key, which is not supported in flat config system.
+
+Flat config uses "languageOptions.globals" to define global variables for your files.
+
+Please see the following page for information on how to convert your config object into the correct format:
+https://eslint.org/docs/latest/use/configure/migration-guide#configuring-language-options
+`,
+
+    ignorePatterns: `
+A config object is using the "ignorePatterns" key, which is not supported in flat config system.
+
+Flat config uses "ignores" to specify files to ignore.
+
+Please see the following page for information on how to convert your config object into the correct format:
+https://eslint.org/docs/latest/use/configure/migration-guide#ignoring-files
+`,
+
+    noInlineConfig: `
+A config object is using the "noInlineConfig" key, which is not supported in flat config system.
+
+Flat config uses "linterOptions.noInlineConfig" to specify files to ignore.
+
+Please see the following page for information on how to convert your config object into the correct format:
+https://eslint.org/docs/latest/use/configure/migration-guide#linter-options
+`,
+
+    overrides: `
+A config object is using the "overrides" key, which is not supported in flat config system.
+
+Flat config is an array that acts like the eslintrc "overrides" array.
+
+Please see the following page for information on how to convert your config object into the correct format:
+https://eslint.org/docs/latest/use/configure/migration-guide#glob-based-configs
+`,
+
+    parser: `
+A config object is using the "parser" key, which is not supported in flat config system.
+
+Flat config uses "languageOptions.parser" to override the default parser.
+
+Please see the following page for information on how to convert your config object into the correct format:
+https://eslint.org/docs/latest/use/configure/migration-guide#custom-parsers
+`,
+
+    parserOptions: `
+A config object is using the "parserOptions" key, which is not supported in flat config system.
+
+Flat config uses "languageOptions.parserOptions" to specify parser options.
+
+Please see the following page for information on how to convert your config object into the correct format:
+https://eslint.org/docs/latest/use/configure/migration-guide#configuring-language-options
+`,
+
+    reportUnusedDisableDirectives: `
+A config object is using the "reportUnusedDisableDirectives" key, which is not supported in flat config system.
+
+Flat config uses "linterOptions.reportUnusedDisableDirectives" to specify files to ignore.
+
+Please see the following page for information on how to convert your config object into the correct format:
+https://eslint.org/docs/latest/use/configure/migration-guide#linter-options
+`,
+
+    root: `
+A config object is using the "root" key, which is not supported in flat config system.
+
+Flat configs always act as if they are the root config file, so this key can be safely removed.
+`
+};
+
+module.exports = function({ key }) {
+
+    return messages[key].trim();
+};