系统设置改为 Tab 布局，并加大备份区块内边距。

Co-authored-by: Cursor <cursoragent@cursor.com>

app.py

@@ -307,13 +307,19 @@ def _handle_wechat_settings(*, send_test: bool = False) -> None:
 def settings_page():
     if request.method == "POST":
         action = (request.form.get("form_action") or "account").strip()
+        return_tab = (request.form.get("return_tab") or "").strip()
         if action == "wechat":
             _handle_wechat_settings(send_test=False)
+            return_tab = return_tab or "wechat"
         elif action == "wechat_test":
             _handle_wechat_settings(send_test=True)
+            return_tab = return_tab or "wechat"
         else:
             _handle_account_settings()
-        return redirect(url_for("settings_page"))
+            return_tab = return_tab or "account"
+        if return_tab not in ("account", "wechat", "backup"):
+            return_tab = "account"
+        return redirect(url_for("settings_page", tab=return_tab))
 
     return render_template(
         "settings.html",