feat(auth): 登录异常改为居中弹窗

test/auth/auth_page_test.dart

@@ -78,6 +78,7 @@ void main() {
 
     expect(find.text('Enter your email'), findsOneWidget);
     expect(find.text('Welcome back'), findsOneWidget);
+    expect(find.byKey(const Key('centered-error-dialog')), findsNothing);
   });
 
   testWidgets(
@@ -94,6 +95,80 @@ void main() {
         find.text('Password needs both letters and numbers'),
         findsOneWidget,
       );
+      expect(find.byKey(const Key('centered-error-dialog')), findsNothing);
+    },
+  );
+
+  testWidgets('should_show_centered_dialog_when_login_api_returns_an_error', (
+    tester,
+  ) async {
+    final api = _FailingAuthApi(loginMessage: 'Invalid email or password');
+    await pumpAuthPage(tester, api: api);
+    await _enterValidCredentials(tester);
+
+    await tester.ensureVisible(find.byKey(const Key('auth-submit')));
+    await tester.tap(find.byKey(const Key('auth-submit')));
+    await tester.pumpAndSettle();
+
+    final dialog = find.byKey(const Key('centered-error-dialog'));
+    expect(dialog, findsOneWidget);
+    expect(find.text('Login failed'), findsOneWidget);
+    expect(find.text('Invalid email or password'), findsOneWidget);
+    expect(api.loginCalls, 1);
+    expect(
+      tester.getCenter(dialog),
+      offsetMoreOrLessEquals(
+        tester.getCenter(find.byType(Scaffold)),
+        epsilon: 1,
+      ),
+    );
+    expect(
+      tester
+          .widget<FilledButton>(find.byKey(const Key('auth-submit')))
+          .onPressed,
+      isNotNull,
+    );
+
+    await tester.tap(find.byKey(const Key('centered-error-confirm')));
+    await tester.pumpAndSettle();
+    expect(dialog, findsNothing);
+  });
+
+  testWidgets(
+    'should_show_registration_failed_title_when_register_api_returns_an_error',
+    (tester) async {
+      final api = _FailingAuthApi(registerMessage: 'Email already exists');
+      await pumpAuthPage(tester, signUp: true, api: api);
+      await _enterValidCredentials(tester);
+
+      await tester.ensureVisible(find.byKey(const Key('auth-submit')));
+      await tester.tap(find.byKey(const Key('auth-submit')));
+      await tester.pumpAndSettle();
+
+      expect(find.byKey(const Key('centered-error-dialog')), findsOneWidget);
+      expect(find.text('Registration failed'), findsOneWidget);
+      expect(find.text('Email already exists'), findsOneWidget);
+      expect(api.registerCalls, 1);
+
+      await tester.tapAt(const Offset(8, 8));
+      await tester.pumpAndSettle();
+      expect(find.byKey(const Key('centered-error-dialog')), findsNothing);
+    },
+  );
+
+  testWidgets(
+    'should_show_network_error_when_login_throws_an_unknown_exception',
+    (tester) async {
+      final api = _FailingAuthApi(loginThrowsUnknown: true);
+      await pumpAuthPage(tester, api: api);
+      await _enterValidCredentials(tester);
+
+      await tester.ensureVisible(find.byKey(const Key('auth-submit')));
+      await tester.tap(find.byKey(const Key('auth-submit')));
+      await tester.pumpAndSettle();
+
+      expect(find.byKey(const Key('centered-error-dialog')), findsOneWidget);
+      expect(find.text('Network error, please try again'), findsOneWidget);
     },
   );
 
@@ -342,6 +417,11 @@ void main() {
   });
 }
 
+Future<void> _enterValidCredentials(WidgetTester tester) async {
+  await tester.enterText(find.byKey(const Key('auth-email')), 'a@b.com');
+  await tester.enterText(find.byKey(const Key('auth-password')), 'abcd1234');
+}
+
 void _expectAboveKeyboard(WidgetTester tester, Key fieldKey, double inset) {
   final screenHeight =
       tester.view.physicalSize.height / tester.view.devicePixelRatio;
@@ -351,6 +431,50 @@ void _expectAboveKeyboard(WidgetTester tester, Key fieldKey, double inset) {
   );
 }
 
+class _FailingAuthApi extends AuthApi {
+  _FailingAuthApi({
+    this.loginMessage = 'login failed',
+    this.registerMessage = 'register failed',
+    this.loginThrowsUnknown = false,
+  }) : super(
+         ApiClient(
+           baseUrl: 'http://127.0.0.1:1',
+           adapter: FakeHttpAdapter((_) async => FakeHttpResponse('{}', 500)),
+         ),
+       );
+
+  final String loginMessage;
+  final String registerMessage;
+  final bool loginThrowsUnknown;
+  int loginCalls = 0;
+  int registerCalls = 0;
+
+  @override
+  Future<AuthSession> login({
+    required String email,
+    required String password,
+    required String deviceId,
+    String platform = '',
+    String appVersion = '',
+  }) async {
+    loginCalls++;
+    if (loginThrowsUnknown) throw StateError('unexpected');
+    throw ApiException(401, loginMessage);
+  }
+
+  @override
+  Future<AuthSession> register({
+    required String email,
+    required String password,
+    required String deviceId,
+    String platform = '',
+    String appVersion = '',
+  }) async {
+    registerCalls++;
+    throw ApiException(409, registerMessage);
+  }
+}
+
 class _PendingAuthApi extends AuthApi {
   _PendingAuthApi()
     : super(

test/auth/phone_auth_sheet_test.dart

@@ -5,6 +5,7 @@ import 'dart:convert';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
+import 'package:fruitshorts/core/data/models/auth_session.dart';
 import 'package:fruitshorts/core/data/remote/api_client.dart';
 import 'package:fruitshorts/core/data/remote/auth_api.dart';
 import 'package:fruitshorts/core/data/services/auth_controller.dart';
@@ -97,6 +98,64 @@ void main() {
 
     expect(find.text('Enter a valid phone number'), findsOneWidget);
     expect(adapter.requests, isEmpty);
+    expect(find.byKey(const Key('centered-error-dialog')), findsNothing);
+  });
+
+  testWidgets('should_show_centered_dialog_when_otp_request_fails', (
+    tester,
+  ) async {
+    final api = _FailingPhoneAuthApi(sendOtpMessage: 'Too many OTP requests');
+    final auth = AuthController(api, AuthSessionStore());
+    await _pumpHost(tester, auth);
+    await tester.tap(find.byKey(const Key('open-phone-sheet')));
+    await tester.pumpAndSettle();
+    await tester.enterText(
+      find.byKey(const Key('auth-phone-number')),
+      '08123456789',
+    );
+
+    await tester.tap(find.byKey(const Key('auth-send-code')));
+    await tester.pumpAndSettle();
+
+    expect(find.byKey(const Key('centered-error-dialog')), findsOneWidget);
+    expect(find.text('Login failed'), findsOneWidget);
+    expect(find.text('Too many OTP requests'), findsOneWidget);
+    expect(api.sendOtpCalls, 1);
+    expect(
+      tester
+          .widget<TextButton>(find.byKey(const Key('auth-send-code')))
+          .onPressed,
+      isNotNull,
+    );
+  });
+
+  testWidgets('should_show_centered_dialog_when_phone_login_fails', (
+    tester,
+  ) async {
+    final api = _FailingPhoneAuthApi(loginMessage: 'Invalid verification code');
+    final auth = AuthController(api, AuthSessionStore());
+    await _pumpHost(tester, auth);
+    await tester.tap(find.byKey(const Key('open-phone-sheet')));
+    await tester.pumpAndSettle();
+    await tester.enterText(
+      find.byKey(const Key('auth-phone-number')),
+      '08123456789',
+    );
+    await tester.enterText(find.byKey(const Key('auth-phone-code')), '123456');
+
+    await tester.tap(find.byKey(const Key('auth-phone-submit')));
+    await tester.pumpAndSettle();
+
+    expect(find.byKey(const Key('centered-error-dialog')), findsOneWidget);
+    expect(find.text('Login failed'), findsOneWidget);
+    expect(find.text('Invalid verification code'), findsOneWidget);
+    expect(api.loginWithPhoneCalls, 1);
+    expect(
+      tester
+          .widget<FilledButton>(find.byKey(const Key('auth-phone-submit')))
+          .onPressed,
+      isNotNull,
+    );
   });
 
   testWidgets('should_keep_code_above_ios_keyboard', (tester) async {
@@ -132,6 +191,45 @@ void main() {
   });
 }
 
+class _FailingPhoneAuthApi extends AuthApi {
+  _FailingPhoneAuthApi({
+    this.sendOtpMessage = 'otp failed',
+    this.loginMessage = 'login failed',
+  }) : super(
+         ApiClient(
+           baseUrl: 'http://127.0.0.1:1',
+           adapter: FakeHttpAdapter((_) async => FakeHttpResponse('{}', 500)),
+         ),
+       );
+
+  final String sendOtpMessage;
+  final String loginMessage;
+  int sendOtpCalls = 0;
+  int loginWithPhoneCalls = 0;
+
+  @override
+  Future<void> sendOtp({
+    required String target,
+    required String scene,
+    required String deviceId,
+  }) async {
+    sendOtpCalls++;
+    throw ApiException(429, sendOtpMessage);
+  }
+
+  @override
+  Future<AuthSession> loginWithPhone({
+    required String target,
+    required String code,
+    required String deviceId,
+    String platform = '',
+    String appVersion = '',
+  }) async {
+    loginWithPhoneCalls++;
+    throw ApiException(401, loginMessage);
+  }
+}
+
 Future<void> _pumpHost(WidgetTester tester, AuthController auth) {
   return tester.pumpWidget(
     MultiProvider(