第一期骨架：登录、实例登记、多机总览、内嵌/新标签打开。

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

templates/base.html

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+<!doctype html>
+<html lang="zh-CN">
+<head>
+  <meta charset="utf-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1">
+  <title>{% block title %}期权中控{% endblock %}</title>
+  <link rel="stylesheet" href="{{ url_for('static', filename='hub.css') }}">
+</head>
+<body>
+  {% if session.get('logged_in') %}
+  <header class="topbar">
+    <div class="brand">crypto_okx_hub</div>
+    <nav>
+      <a href="/" class="{% if request.path == '/' %}active{% endif %}">总览</a>
+      <a href="/instances" class="{% if request.path.startswith('/instances') %}active{% endif %}">实例</a>
+      <a href="/desk" class="{% if request.path.startswith('/desk') %}active{% endif %}">工作台</a>
+      <a href="/logout">退出</a>
+    </nav>
+  </header>
+  {% endif %}
+  <main class="main">
+    {% with messages = get_flashed_messages() %}
+      {% if messages %}<div class="flash">{{ messages[0] }}</div>{% endif %}
+    {% endwith %}
+    {% block body %}{% endblock %}
+  </main>
+  {% block scripts %}{% endblock %}
+</body>
+</html>