Add logout control and show a single locked underlying on hedge select.

Nav gains an exit link when auth is enabled; PO option picker no longer shows unused ETH/BTC toggles.

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

lib/instance/templates/embed_shell.html

@@ -7,8 +7,8 @@
     <script src="/static/autofill_guard.js?v=1"></script>
     <link rel="stylesheet" href="/static/instance_theme_early.css?v=4">
     <link rel="stylesheet" href="/static/account_risk_badge.css?v=4">
-    <link rel="stylesheet" href="/static/instance_page.css?v=27">
-    <link rel="stylesheet" href="/static/instance_theme.css?v=123">
+    <link rel="stylesheet" href="/static/instance_page.css?v=28">
+    <link rel="stylesheet" href="/static/instance_theme.css?v=124">
     <script src="/static/account_risk_badge.js?v=4"></script>
     <script src="/static/open_submit_gate.js?v=1"></script>
     <meta name="theme-color" content="#0b0d14">
@@ -29,6 +29,9 @@
 <div class="container">
     {% include 'instance_brand_header.html' %}
     <nav class="top-nav embed-top-nav" aria-label="实例导航">
+        {% if not auth_disabled %}
+        <a href="/logout" class="top-nav-logout" title="退出登录">退出</a>
+        {% endif %}
         <div class="top-nav-links">
         {% if hedge_plan_nav_visible and display.show_nav_hedge_plan %}
         <a href="/hedge-plan" data-embed-tab="hedge_plan" class="{% if initial_tab == 'hedge_plan' %}active{% endif %}">{% if hedge_plan_show_options_options %}期期对冲{% else %}永期对冲{% endif %}</a>