feat(account): 增加账号中心页面逻辑

lib/pages/account/account_deactivate_logic.dart

@@ -0,0 +1,85 @@
+// Author: fruit.com.cn
+
+import 'package:flutter/foundation.dart';
+
+import '../../core/data/remote/api_client.dart';
+import '../../core/data/repositories/account_repository.dart';
+
+/// 注销申请与撤销状态。
+class AccountDeactivateLogic extends ChangeNotifier {
+  AccountDeactivateLogic(
+    this._repository, {
+    required this.clearSession,
+  });
+
+  static const maxReasonLength = 200;
+
+  final AccountRepository _repository;
+  final Future<void> Function() clearSession;
+  DateTime? scheduledAt;
+  bool requesting = false;
+  bool cancelling = false;
+  String? error;
+  String? actionMessage;
+  bool cancelSucceeded = false;
+  bool _disposed = false;
+
+  /// 申请注销；成功后立即清理本地会话。
+  Future<bool> request(String reason) async {
+    requesting = true;
+    error = null;
+    cancelSucceeded = false;
+    _notify();
+    try {
+      scheduledAt = await _repository.deactivate(
+        reason.trim().substring(
+          0,
+          reason.trim().length > maxReasonLength
+              ? maxReasonLength
+              : reason.trim().length,
+        ),
+      );
+      await clearSession();
+      return true;
+    } catch (failure) {
+      error = failure is ApiException
+          ? failure.message
+          : 'accountDeactivateFailed';
+      return false;
+    } finally {
+      requesting = false;
+      _notify();
+    }
+  }
+
+  /// 撤销待处理申请；失败时保留后端文案。
+  Future<bool> cancel() async {
+    cancelling = true;
+    actionMessage = null;
+    cancelSucceeded = false;
+    _notify();
+    try {
+      await _repository.cancelDeactivation();
+      cancelSucceeded = true;
+      return true;
+    } catch (failure) {
+      actionMessage = failure is ApiException
+          ? failure.message
+          : 'accountCancelFailed';
+      return false;
+    } finally {
+      cancelling = false;
+      _notify();
+    }
+  }
+
+  void _notify() {
+    if (!_disposed) notifyListeners();
+  }
+
+  @override
+  void dispose() {
+    _disposed = true;
+    super.dispose();
+  }
+}