fix: Implement Network-First SW strategy, no-cache headers in Nginx for index.html/sw.js, and auto 401 token cleanup to fix post-redeploy stale cache issues

frontend/src/api/client.js

@@ -30,6 +30,9 @@ export const apiFetch = async (endpoint, options = {}) => {
   }
 
   if (!response.ok) {
+    if (response.status === 401) {
+      setAuthToken(null);
+    }
     let errorMsg = 'Ein Fehler ist aufgetreten.';
     if (data) {
       if (typeof data.error === 'string') errorMsg = data.error;