Update Pro dummy webpack config to use forEach pattern

The findIndex approach with '.scss'.match(config.test) was failing
in Shakapacker 9.1.0 because the webpack rule structure changed.

Updated Pro dummy to use the same forEach pattern as main dummy:
- Tests both 'example.scss' and 'example.module.scss'
- Safely checks if rule.use is an array before pushing
- Handles both regular SCSS and CSS Module SCSS files

This fixes the build error:
"TypeError: Cannot read properties of undefined (reading 'push')"

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: justin808

react_on_rails_pro/spec/dummy/config/webpack/commonWebpackConfig.js

@@ -26,10 +26,13 @@ const sassLoaderConfig = {
 };
 
 const baseClientWebpackConfig = generateWebpackConfig();
-const scssConfigIndex = baseClientWebpackConfig.module.rules.findIndex((config) =>
-  '.scss'.match(config.test),
-);
-baseClientWebpackConfig.module.rules[scssConfigIndex].use.push(sassLoaderConfig);
+
+// Add sass-resources-loader to all SCSS rules (both .scss and .module.scss)
+baseClientWebpackConfig.module.rules.forEach((rule) => {
+  if (Array.isArray(rule.use) && rule.test && (rule.test.test('example.scss') || rule.test.test('example.module.scss'))) {
+    rule.use.push(sassLoaderConfig);
+  }
+});
 
 if (isHMR) {
   baseClientWebpackConfig.plugins.push(