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/presentation/js_api.dart

@@ -0,0 +1,87 @@
+import 'dart:async';
+import 'dart:convert';
+
+import 'package:dsbridge_flutter/dsbridge_flutter.dart';
+import 'package:flutter/material.dart';
+import 'package:package_info_plus/package_info_plus.dart';
+
+import 'js_api_result.dart';
+
+class JsApi extends JavaScriptNamespaceInterface {
+  JsApi({
+    this.onClose,
+    this.onLoginRequested,
+    this.onMallStateChanged,
+    Future<String> Function()? appVersionResolver,
+  }) : _appVersionResolver = appVersionResolver ?? _readAppVersion;
+
+  final VoidCallback? onClose;
+  final VoidCallback? onLoginRequested;
+  final ValueChanged<Map<dynamic, dynamic>?>? onMallStateChanged;
+  final Future<String> Function() _appVersionResolver;
+
+  @override
+  void register() {
+    registerFunction(close);
+    registerFunction(getAppVersion);
+    registerFunction(mallStateChanged);
+    registerFunction(login);
+  }
+
+  @pragma('vm:entry-point')
+  void close(dynamic arg, CompletionHandler handler) {
+    onClose?.call();
+    handler.complete(const JsApiResult.success().toMap());
+  }
+
+  @pragma('vm:entry-point')
+  void getAppVersion(dynamic arg, CompletionHandler handler) {
+    unawaited(_completeAppVersion(handler));
+  }
+
+  Future<void> _completeAppVersion(CompletionHandler handler) async {
+    try {
+      final version = await _appVersionResolver();
+      handler.complete(
+        JsApiResult(
+          code: 0,
+          message: 'success',
+          data: <String, dynamic>{'version': version},
+        ).toMap(),
+      );
+    } catch (_) {
+      handler.complete(
+        const JsApiResult(code: 1, message: 'app version unavailable').toMap(),
+      );
+    }
+  }
+
+  static Future<String> _readAppVersion() async =>
+      (await PackageInfo.fromPlatform()).version;
+
+  @pragma('vm:entry-point')
+  void mallStateChanged(dynamic arg, CompletionHandler handler) {
+    onMallStateChanged?.call(coerceMallStateMap(arg));
+    handler.complete(const JsApiResult.success().toMap());
+  }
+
+  @pragma('vm:entry-point')
+  void login(dynamic arg, CompletionHandler handler) {
+    onLoginRequested?.call();
+    handler.complete(const JsApiResult.success().toMap());
+  }
+}
+
+Map<dynamic, dynamic>? coerceMallStateMap(dynamic arg) {
+  if (arg is Map) return arg;
+  if (arg is String && arg.isNotEmpty) {
+    try {
+      final decoded = jsonDecode(arg);
+      if (decoded is Map) return decoded;
+    } catch (_) {}
+  }
+  if (arg is List && arg.isNotEmpty && arg.first is Map) {
+    return arg.first as Map<dynamic, dynamic>;
+  }
+  return null;
+}