refactor: 拆分主页与公共组件，扫码登录改走 WinHTTP

- 抽出 lib/core 的日期/JSON 工具，收敛各页重复解析
- 主页与音乐风险页拆成组件，风险功能共用一套运行框架
- 修复设置页作为主页页签保存时弹掉根路由导致的黑屏
- 登录对齐 Astral aimedb 协议：84 位二维码校验、签名与请求头修正，
  补 GlobalSign 中间证书；Windows 改用 WinHTTP 绕过服务端对
  BoringSSL 的 TLS 指纹拦截（证书校验保持开启）
- 补开发预览数据与测试

test/home_lazy_tabs_test.dart

@@ -0,0 +1,78 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:ichino/config/strings.dart';
+import 'package:ichino/config/title_server_config.dart';
+import 'package:ichino/dev/ui_preview_data.dart';
+import 'package:ichino/models/session_model.dart';
+import 'package:ichino/pages/about_page.dart';
+import 'package:ichino/pages/best50_page.dart';
+import 'package:ichino/pages/high_risk_feature_page.dart';
+import 'package:ichino/pages/home/home_tab_view.dart';
+import 'package:ichino/pages/home_page.dart';
+import 'package:ichino/pages/settings_page.dart';
+import 'package:ichino/pages/ticket_page.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+void main() {
+  setUp(() async {
+    SharedPreferences.setMockInitialValues({});
+    await TitleServerConfigHolder().clear();
+    SessionModel.instance.reset();
+  });
+
+  testWidgets('主页启动时只构建首页，其他页签首次访问才创建', (tester) async {
+    await tester.pumpWidget(
+      const MaterialApp(home: HomePage(userId: 1, token: 't')),
+    );
+    await tester.pump();
+
+    expect(find.byType(HomeTabView), findsOneWidget);
+    expect(find.byType(TicketPage), findsNothing);
+    expect(find.byType(Best50Page), findsNothing);
+    expect(find.byType(HighRiskFeaturePage), findsNothing);
+    expect(find.byType(SettingsPage), findsNothing);
+    expect(find.byType(AboutPage), findsNothing);
+
+    await tester.tap(find.byIcon(Icons.bar_chart_outlined));
+    await tester.pump();
+
+    expect(find.byType(Best50Page), findsOneWidget);
+    expect(find.widgetWithText(AppBar, AppStrings.tabBest50), findsOneWidget);
+    // 其余页签仍未构建。
+    expect(find.byType(TicketPage), findsNothing);
+    expect(find.byType(SettingsPage), findsNothing);
+
+    await tester.tap(find.byIcon(Icons.settings_outlined));
+    await tester.pump();
+
+    expect(find.byType(SettingsPage), findsOneWidget);
+    // 已访问过的页签保留在 IndexedStack 里，切换回来不重建。
+    expect(find.byType(Best50Page, skipOffstage: false), findsOneWidget);
+    expect(find.byType(TicketPage), findsNothing);
+  });
+
+  testWidgets('有预览种子数据时，未配置 Title Server 也展示主页数据', (tester) async {
+    tester.view.physicalSize = const Size(1280, 1600);
+    tester.view.devicePixelRatio = 1.0;
+    addTearDown(tester.view.reset);
+
+    await tester.pumpWidget(
+      const MaterialApp(
+        home: HomePage(
+          userId: uiPreviewUserId,
+          token: uiPreviewToken,
+          restored: SessionRestoreResult(
+            reusedCookie: true,
+            userData: uiPreviewUserData,
+            preview: uiPreviewPreview,
+            loggedIn: true,
+          ),
+        ),
+      ),
+    );
+    await tester.pump();
+
+    expect(find.text(AppStrings.titleServerNotConfigured), findsNothing);
+    expect(find.text('Ichino'), findsOneWidget);
+  });
+}