Disable Astro's default locale redirect to allow custom language detection

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

astro.config.mjs

@@ -14,6 +14,7 @@ export default defineConfig({
     locales: ['cs', 'en'],
     routing: {
       prefixDefaultLocale: true,
+      redirectToDefaultLocale: false,
     },
   },
 });