chore: update VPS IP address to 198.252.101.35

frontend/lib/core/network/api_constants.dart

@@ -5,7 +5,7 @@ import 'package:shared_preferences/shared_preferences.dart';
 class ApiConstants {
   static const int port = 18484;
   static const String tunnelUrl = 'https://tis-rms.cc.cd/api';
-  static const String vpsUrl = 'http://198.252.107.197:$port/api';
+  static const String vpsUrl = 'http://198.252.101.35:$port/api';
   static const String localhostUrl = 'http://127.0.0.1:$port/api';
 
   // Runtime-mutable base URL — set by ServerDiscoveryService before first use.

frontend/lib/ui/screens/login/login_screen.dart

@@ -540,7 +540,7 @@ class _LoginScreenState extends ConsumerState<LoginScreen> with SingleTickerProv
               controller: controller,
               decoration: InputDecoration(
                 labelText: 'Server URL',
-                hintText: 'http://198.252.107.197:18484/api',
+                hintText: 'http://198.252.101.35:18484/api',
                 border: OutlineInputBorder(
                   borderRadius: BorderRadius.circular(10),
                 ),