总览北京时间改为更易读的纯文本样式，日期格式与拉取时间一致。

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

templates/dashboard.html

@@ -3,9 +3,9 @@
 {% block body %}
 <section class="page-head">
   <h1>期权持仓总览</h1>
-  <div class="overview-bj-clock" id="overview-bj-clock" title="北京时间">
+  <div class="overview-bj-clock" id="overview-bj-clock" title="Asia/Shanghai">
     <span class="overview-bj-label">北京时间</span>
-    <span class="overview-bj-time" id="overview-bj-time">--:--:--</span>
+    <time class="overview-bj-time" id="overview-bj-time" datetime="">--</time>
   </div>
   <button type="button" class="btn" id="btn-refresh">刷新</button>
 </section>
@@ -13,6 +13,6 @@
 <div id="overview-grid"></div>
 {% endblock %}
 {% block scripts %}
-<script src="{{ url_for('static', filename='hub.js') }}?v=2"></script>
+<script src="{{ url_for('static', filename='hub.js') }}?v=3"></script>
 <script>HubOverview.boot();</script>
 {% endblock %}