feat: 对齐常驻商城与七鱼客服交互

- 同步商城 H5 登录态与原生 token
- 完善商城/原生 tab 切换、动画及返回交互
- 修复七鱼客服键盘避让和状态栏恢复
- 调整开屏跳过按钮与登录入口交互

lib/features/web/application/web_navigation_policy.dart

@@ -0,0 +1,38 @@
+/// Mall pages stay in the resident WebView unless H5 explicitly requests an
+/// external handoff or the URI is handled by the operating system.
+bool shouldOpenWebUrlExternally(String rawUrl) {
+  final uri = Uri.tryParse(rawUrl);
+  if (uri == null) return false;
+  return const {'tel', 'mailto', 'sms'}.contains(uri.scheme.toLowerCase()) ||
+      uri.queryParameters.containsKey('out');
+}
+
+Uri sanitizeSystemCommunicationUri(Uri uri) {
+  if (uri.scheme.toLowerCase() != 'tel') return uri;
+  final parameterMarker = uri.path.indexOf('&');
+  final phone = parameterMarker < 0
+      ? uri.path
+      : uri.path.substring(0, parameterMarker);
+  return Uri(scheme: uri.scheme, path: phone);
+}
+
+bool isTrustedQiyuUrl(String rawUrl) {
+  final uri = Uri.tryParse(rawUrl);
+  if (uri == null ||
+      (uri.scheme != 'http' && uri.scheme != 'https') ||
+      uri.host.isEmpty) {
+    return false;
+  }
+  final host = uri.host.toLowerCase();
+  return host == 'qiyukf.com' ||
+      host.endsWith('.qiyukf.com') ||
+      host == 'qiyukf.cn' ||
+      host.endsWith('.qiyukf.cn');
+}
+
+bool shouldApplyQiyuSafeArea(String rawUrl) => isTrustedQiyuUrl(rawUrl);
+
+bool isQiyuClientEntryUrl(String rawUrl) {
+  final path = Uri.tryParse(rawUrl)?.path;
+  return path == '/client' || (path?.startsWith('/client/') ?? false);
+}