fix(i18n): harden locale validation and fix missing translation tags

i18n/request.ts

@@ -2,11 +2,18 @@ import { getRequestConfig } from 'next-intl/server';
 import * as Sentry from '@sentry/nextjs';
 
 export default getRequestConfig(async ({ requestLocale }) => {
-  let locale = await requestLocale;
+  // Hardened locale validation: only allow 'en' or 'de'
+  // Use a temporary variable to validate before assigning to locale
+  const rawLocale = await requestLocale;
+  const supportedLocales = ['en', 'de'];
+  const locale =
+    typeof rawLocale === 'string' && supportedLocales.includes(rawLocale) ? rawLocale : 'en';
 
-  // Ensure that a valid locale is used
-  if (!locale || !['en', 'de'].includes(locale)) {
-    locale = 'en';
+  // Log to Sentry if we had to fallback, as it might indicate a routing issue
+  if (!rawLocale || !supportedLocales.includes(rawLocale as string)) {
+    console.warn(
+      `[i18n] Invalid or missing requestLocale received: "${rawLocale}". Falling back to "en".`,
+    );
   }
 
   return {
@@ -26,6 +33,6 @@ export default getRequestConfig(async ({ requestLocale }) => {
         return path;
       }
       return 'fallback';
-    }
+    },
   } as any;
 });