feat(useragent): added connection info setup screen

useragent/lib/providers/server_info.dart

@@ -0,0 +1,51 @@
+import 'package:arbiter/features/server_info_storage.dart';
+import 'package:cryptography/cryptography.dart';
+import 'package:riverpod_annotation/riverpod_annotation.dart';
+
+part 'server_info.g.dart';
+
+@riverpod
+ServerInfoStorage serverInfoStorage(Ref ref) {
+  return const SecureServerInfoStorage();
+}
+
+@Riverpod(keepAlive: true)
+class ServerInfo extends _$ServerInfo {
+  @override
+  Future<StoredServerInfo?> build() {
+    final storage = ref.watch(serverInfoStorageProvider);
+    return storage.load();
+  }
+
+  Future<void> save({
+    required String address,
+    required int port,
+    required List<int> caCert,
+  }) async {
+    final storage = ref.read(serverInfoStorageProvider);
+    final fingerprint = await _fingerprint(caCert);
+    final serverInfo = StoredServerInfo(
+      address: address,
+      port: port,
+      caCertFingerprint: fingerprint,
+    );
+
+    state = await AsyncValue.guard(() async {
+      await storage.save(serverInfo);
+      return serverInfo;
+    });
+  }
+
+  Future<void> clear() async {
+    final storage = ref.read(serverInfoStorageProvider);
+    state = await AsyncValue.guard(() async {
+      await storage.clear();
+      return null;
+    });
+  }
+
+  Future<String> _fingerprint(List<int> caCert) async {
+    final digest = await Sha256().hash(caCert);
+    return digest.bytes.map((byte) => byte.toRadixString(16).padLeft(2, '0')).join();
+  }
+}