Add public key to peer info and implement public key generation from private key

lib/services/vpn_session_service.dart

@@ -46,6 +46,19 @@ class VpnSessionService {
     }
   }
   
+  /// Generates public key from private key
+  static Future<String> _getPublicKeyFromPrivateKey(String privateKey) async {
+    try {
+      final pubProcess = await Process.start('wg', ['pubkey']);
+      pubProcess.stdin.writeln(privateKey);
+      await pubProcess.stdin.close();
+      final publicKey = await pubProcess.stdout.transform(utf8.decoder).join();
+      return publicKey.trim();
+    } catch (e) {
+      return 'Error generating public key: $e';
+    }
+  }
+
   /// Gets keepalive info for a specific peer
   static Future<String> _getKeepaliveForPeer(String publicKey) async {
     try {