中控总览改为后台常驻并行拉取热缓存，浏览器只读缓存并经 SSE 更新。

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

templates/dashboard.html

@@ -15,6 +15,6 @@
 <div id="overview-grid"></div>
 {% endblock %}
 {% block scripts %}
-<script src="{{ url_for('static', filename='hub.js') }}?v=28"></script>
+<script src="{{ url_for('static', filename='hub.js') }}?v=29"></script>
 <script>HubOverview.boot();</script>
 {% endblock %}