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_back_navigation.dart

@@ -0,0 +1,53 @@
+typedef WebCanGoBack = Future<bool> Function();
+typedef WebGoBack = Future<void> Function();
+typedef WebRunJavaScriptReturningResult = Future<Object> Function(String code);
+
+const visibleWebBackControlJavaScript = r'''
+(() => {
+  const selectors = [
+    '.back-btn',
+    '[aria-label="返回"]',
+    '[aria-label="Back"]',
+    '[title="返回"]',
+    '[title="Back"]',
+  ].join(',');
+  const candidates = Array.from(document.querySelectorAll(selectors));
+  const control = candidates.find((element) => {
+    const rect = element.getBoundingClientRect();
+    const style = window.getComputedStyle(element);
+    if (
+      rect.width <= 0 || rect.height <= 0 || rect.bottom <= 0 ||
+      rect.right <= 0 || rect.top >= window.innerHeight ||
+      rect.left >= window.innerWidth || style.display === 'none' ||
+      style.visibility === 'hidden' || style.pointerEvents === 'none' ||
+      Number(style.opacity || 1) <= 0
+    ) return false;
+    const x = Math.min(Math.max(rect.left + rect.width / 2, 0), window.innerWidth - 1);
+    const y = Math.min(Math.max(rect.top + rect.height / 2, 0), window.innerHeight - 1);
+    const topElement = document.elementFromPoint(x, y);
+    return topElement !== null && (topElement === element || element.contains(topElement));
+  });
+  if (!control) return false;
+  control.click();
+  return true;
+})()
+''';
+
+Future<bool> tryGoBackInWebHistory({
+  required WebCanGoBack canGoBack,
+  required WebGoBack goBack,
+}) async {
+  if (!await canGoBack()) return false;
+  await goBack();
+  return true;
+}
+
+Future<bool> tryGoBackUsingVisibleWebControl({
+  required WebRunJavaScriptReturningResult runJavaScriptReturningResult,
+}) async {
+  final result = await runJavaScriptReturningResult(
+    visibleWebBackControlJavaScript,
+  );
+  if (result is bool) return result;
+  return result.toString().replaceAll('"', '').trim().toLowerCase() == 'true';
+}