linting: add commonjs globals override for *.cjs files

lib/eslint.config.js

@@ -225,6 +225,19 @@ export default tseslint.config(
     },
   },
 
+  // CommonJS configuration files (e.g., postcss.config.cjs)
+  // Provides Node.js globals (module, require, etc.) that were previously
+  // included via eslint-config-standard in ESLint v8
+  {
+    files: ['**/*.cjs'],
+    languageOptions: {
+      globals: {
+        ...globals.node,
+      },
+      sourceType: 'commonjs',
+    },
+  },
+
   // Prettier recommended config (should be last to override other formatting rules)
   eslintPluginPrettierRecommended,
 )