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/mall_bridge_state.dart

@@ -0,0 +1,67 @@
+import 'package:flutter/foundation.dart';
+
+enum MallBridgeTab { home, market, orders, profile }
+
+class MallBridgeState {
+  const MallBridgeState({
+    this.ready = false,
+    this.activeTab = MallBridgeTab.home,
+    this.canGoBack = false,
+  });
+
+  final bool ready;
+  final MallBridgeTab activeTab;
+  final bool canGoBack;
+}
+
+class MallBridgeController {
+  MallBridgeController._();
+
+  static final instance = MallBridgeController._();
+
+  final state = ValueNotifier(const MallBridgeState());
+  Future<void> Function(MallBridgeTab tab, bool reselect)? _activateTab;
+  Future<void> Function()? _goBack;
+
+  void attach({
+    required Future<void> Function(MallBridgeTab tab, bool reselect)
+    activateTab,
+    required Future<void> Function() goBack,
+  }) {
+    _activateTab = activateTab;
+    _goBack = goBack;
+  }
+
+  void detach() {
+    _activateTab = null;
+    _goBack = null;
+    state.value = const MallBridgeState();
+  }
+
+  void update(Map<dynamic, dynamic>? raw) {
+    final tab = MallBridgeTab.values.firstWhere(
+      (item) => item.name == raw?['activeTab'],
+      orElse: () => MallBridgeTab.home,
+    );
+    state.value = MallBridgeState(
+      ready: _asBool(raw?['ready']),
+      activeTab: tab,
+      canGoBack: _asBool(raw?['canGoBack']),
+    );
+  }
+
+  Future<void> activate(MallBridgeTab tab, {bool reselect = false}) async {
+    final current = state.value;
+    state.value = MallBridgeState(
+      ready: current.ready,
+      activeTab: tab,
+      canGoBack: current.canGoBack,
+    );
+    await _activateTab?.call(tab, reselect);
+  }
+
+  Future<void> goBack() async => await _goBack?.call();
+}
+
+bool _asBool(Object? value) =>
+    value == true || value == 1 || value == '1' || value == 'true';