refactor(client): widgets 颜色迁移到 context.tokens

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

client/test/write_guard_test.dart

@@ -3,6 +3,7 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:jiu_client/core/auth/auth_state.dart';
 import 'package:jiu_client/core/config/license_copy.dart';
+import 'package:jiu_client/core/theme/themes.dart';
 import 'package:jiu_client/models/license.dart';
 import 'package:jiu_client/providers/license_provider.dart';
 import 'package:jiu_client/widgets/write_guard.dart';
@@ -37,6 +38,7 @@ Widget _harness({
       licenseProvider.overrideWith(() => _FakeLicenseNotifier(lic)),
     ],
     child: MaterialApp(
+      theme: buildTheme('a'),
       home: Scaffold(
         body: WriteGuard(
           child: ElevatedButton(