Fix CSS modules to use default exports for ReScript compatibility

Shakapacker 9 changed CSS modules default to namedExport: true, but
the existing ReScript code expects default exports (import css from).

Changes:
- Set namedExport: false for all CSS loaders
- Change exportLocalsConvention from camelCaseOnly to camelCase
- Apply fix to all CSS-related rules, not just SCSS

This resolves SSR errors: "Cannot read properties of undefined
(reading 'elementEnter')" in ReScript components.

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

Co-Authored-By: Claude <noreply@anthropic.com>

Author: justin808

config/rspack/commonRspackConfig.js

@@ -20,6 +20,22 @@ const ignoreWarningsConfig = {
   ignoreWarnings: [/Module not found: Error: Can't resolve 'react-dom\/client'/],
 };
 
+// Fix all CSS-related loaders to use default exports instead of named exports
+// Shakapacker 9 defaults to namedExport: true, but existing code expects default exports
+baseClientRspackConfig.module.rules.forEach((rule) => {
+  if (rule.use && Array.isArray(rule.use)) {
+    const cssLoader = rule.use.find((loader) => {
+      const loaderName = typeof loader === 'string' ? loader : loader?.loader;
+      return loaderName?.includes('css-loader');
+    });
+
+    if (cssLoader?.options?.modules) {
+      cssLoader.options.modules.namedExport = false;
+      cssLoader.options.modules.exportLocalsConvention = 'camelCase';
+    }
+  }
+});
+
 const scssConfigIndex = baseClientRspackConfig.module.rules.findIndex((config) =>
   '.scss'.match(config.test) && config.use,
 );
@@ -51,17 +67,6 @@ if (scssConfigIndex === -1) {
     }
   }
 
-  // Fix css-loader configuration for CSS modules if namedExport is enabled
-  // When namedExport is true, exportLocalsConvention must be camelCaseOnly or dashesOnly
-  const cssLoader = scssRule.use.find((loader) => {
-    const loaderName = typeof loader === 'string' ? loader : loader?.loader;
-    return loaderName?.includes('css-loader');
-  });
-
-  if (cssLoader?.options?.modules?.namedExport) {
-    cssLoader.options.modules.exportLocalsConvention = 'camelCaseOnly';
-  }
-
   baseClientRspackConfig.module.rules[scssConfigIndex].use.push(sassLoaderConfig);
 }