feat: persist server settings

lib/data/sources/local/credential_store.dart

@@ -1,10 +1,14 @@
 import 'package:flutter_secure_storage/flutter_secure_storage.dart';
 
+import '../../../domain/models/server_config.dart';
+
 typedef Credentials = ({String username, String password});
 
 class CredentialStore {
   static const _usernameKey = 'localiserd_username';
   static const _passwordKey = 'localiserd_password';
+  static const _hostKey = 'localiserd_host';
+  static const _portKey = 'localiserd_port';
 
   final _storage = const FlutterSecureStorage();
 
@@ -24,8 +28,28 @@ class CredentialStore {
     return (username: username, password: password);
   }
 
+  Future<void> saveServer(ServerConfig config) => Future.wait([
+        _storage.write(key: _hostKey, value: config.host),
+        _storage.write(key: _portKey, value: config.port.toString()),
+      ]).then((_) {});
+
+  Future<ServerConfig?> loadServer() async {
+    final results = await Future.wait([
+      _storage.read(key: _hostKey),
+      _storage.read(key: _portKey),
+    ]);
+    final host = results[0];
+    final portStr = results[1];
+    if (host == null || portStr == null) return null;
+    final port = int.tryParse(portStr);
+    if (port == null) return null;
+    return ServerConfig(host: host, port: port);
+  }
+
   Future<void> clear() => Future.wait([
         _storage.delete(key: _usernameKey),
         _storage.delete(key: _passwordKey),
+        _storage.delete(key: _hostKey),
+        _storage.delete(key: _portKey),
       ]).then((_) {});
 }