feat: Redux zur Verwaltung des Admin-Status hinzugefügt

- Neuen Redux-Slice 'authSlice' erstellt, um den Admin-Login-Status zu verwalten.
- Token-Verwaltung im SettingsModal angepasst, um Redux-Status zu aktualisieren.
- Admin-Warnhinweis im Header zeigt jetzt den Redux-Status an und aktualisiert sich automatisch.
- Abmeldefunktion verbessert, um Token aus dem Redux-Store zu entfernen und Seite zu aktualisieren.

components/Header.jsx

@@ -1,6 +1,5 @@
-// components/Header.jsx
-"use client";
-import React, { useState } from "react";
+"use client"; // components/Header.jsx
+import React, { useState, useEffect } from "react";
 import Image from "next/image";
 import { useRouter } from "next/router";
 import "bootstrap-icons/font/bootstrap-icons.css";
@@ -8,13 +7,33 @@ import SettingsModal from "./modales/settingsModal/SettingsModal";
 import { useSelector } from "react-redux";
 
 function Header() {
+  const isAdminLoggedIn = useSelector((state) => state.auth.isAdminLoggedIn);
   const router = useRouter();
   const deviceName = useSelector((state) => state.variables.deviceName);
   const [showSettingsModal, setShowSettingsModal] = useState(false);
+  //const [isAdminLoggedIn, setIsAdminLoggedIn] = useState(false);
 
   const handleSettingsClick = () => setShowSettingsModal(true);
   const handleCloseSettingsModal = () => setShowSettingsModal(false);
-  const handleLogout = () => (window.location.href = "/offline.html");
+  const handleLogout = () => {
+    localStorage.removeItem("token"); // Token entfernen beim Abmelden
+    //setIsAdminLoggedIn(false);
+    window.location.href = "/offline.html";
+  };
+
+  // Funktion, um den Token-Status zu prüfen
+  useEffect(() => {
+    const token = localStorage.getItem("token");
+    if (token) {
+      const { exp } = JSON.parse(atob(token));
+      if (Date.now() < exp) {
+        //setIsAdminLoggedIn(true);
+      } else {
+        localStorage.removeItem("token"); // Entferne abgelaufenen Token
+        //setIsAdminLoggedIn(false);
+      }
+    }
+  }, []);
 
   return (
     <header className="bg-gray-300 flex justify-between items-center w-full h-28 relative text-black">
@@ -36,6 +55,7 @@ function Header() {
           <p className="text-base text-gray-600">{deviceName}</p>
         </div>
       </div>
+
       <div className="p-4 w-full lg:w-full flex flex-row gap-4 justify-between">
         <div className="flex items-center justify-end w-full">
           <button
@@ -54,6 +74,14 @@ function Header() {
           </button>
         </div>
       </div>
+
+      {/* Warnhinweis, wenn der Admin angemeldet ist */}
+      {isAdminLoggedIn && (
+        <div className="absolute top-0 left-0 w-full h-8 bg-yellow-400 text-center py-2 text-black font-bold">
+          Admin-Modus aktiv
+        </div>
+      )}
+
       {showSettingsModal && (
         <SettingsModal
           showModal={showSettingsModal}