fix(hub): merge mark price from Flask snapshot and fix board refresh

Sync hub positions with instance price_snapshot (order_prices and position_marks).
Fix monitor board UI when hub restarts (version rewind) and queue snapshot fetches.
Expose board aggregate status on /api/ping for diagnostics.

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

manual_trading_hub/static/index.html

@@ -245,6 +245,6 @@
   <div id="toast"></div>
   <script src="https://unpkg.com/lightweight-charts@4.2.0/dist/lightweight-charts.standalone.production.js"></script>
   <script src="/assets/chart.js?v=20260603-hub-binance-tick"></script>
-  <script src="/assets/app.js?v=20260604-hub-mark-price2"></script>
+  <script src="/assets/app.js?v=20260604-hub-board-refresh"></script>
 </body>
 </html>