feat: Centralize authentication redirects to middleware, remove client-side redirect logic, and refine logout process.

src/app/(agent)/layout.tsx

@@ -18,10 +18,11 @@ export default function AgentLayout({
   useEffect(() => {
     if (status === 'loading') return;
 
-    if (!session) {
-      router.replace('/login');
-      return;
-    }
+    // Don't redirect to /login here — the middleware handles that.
+    // Doing it here causes race conditions during logout (layout detects
+    // session loss and redirects to /login via client-side navigation,
+    // which can conflict with the server-side logout redirect).
+    if (!session) return;
 
     // Redirect non-agents to user dashboard
     const userRole = (session.user as any)?.role;