fix: improve server connection handling during authentication

- Updated AuthStateManager to clear the active server ID upon logout, ensuring a proper return to the server connection page.
- Enhanced RouterNotifier to allow users to stay on the server connection page if authenticated, improving navigation flow.
- Modified AuthenticationPage to navigate back to the server connection page instead of popping the navigation stack, enhancing user experience during server setup.

lib/core/router/app_router.dart

@@ -87,10 +87,13 @@ class RouterNotifier extends ChangeNotifier {
     final authState = ref.read(authNavigationStateProvider);
     final connectivityService = ref.read(connectivityServiceProvider);
 
+    // Allow staying on server connection page
     if (location == Routes.serverConnection) {
+      // If authenticated but on server connection page, go to chat
+      // Otherwise stay on server connection page (for back navigation)
       return authState == AuthNavigationState.authenticated
           ? Routes.chat
-          : Routes.authentication;
+          : null;
     }
 
     // Check connectivity status to determine if we should show connection issue