feat: fix logout button, inactivity tracker, and concurrent session termination

shop/components/NavbarClient.tsx

@@ -7,6 +7,7 @@ import { createBrowserClient } from "@supabase/ssr";
 import { type User } from "@supabase/supabase-js";
 import { Rocket, Menu, X, User as UserIcon, LogOut } from "lucide-react";
 import { Button } from "@/components/ui/button";
+import { signOut } from "@/lib/actions/auth";
 
 interface NavbarClientProps {
   user: User | null;
@@ -93,6 +94,11 @@ export function NavbarClient({ user, role = "partner" }: NavbarClientProps) {
   }, []);
 
   const handleSignOut = async () => {
+    try {
+      await signOut();
+    } catch (e) {
+      console.error("Fehler beim Server-Signout:", e);
+    }
     await supabase.auth.signOut();
     setCurrentUser(null);
     setIsMobileMenuOpen(false);