Add clear-and-refetch for hub K-line cache.

Force refresh wipes the series in hub_kline.db before pulling from the exchange; add a Linux clear script and rename the UI button to 清库重拉.

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

manual_trading_hub/static/chart.js

@@ -2648,6 +2648,7 @@
         (data.from_cache || 0) +
         " / 新拉 " +
         (data.fetched || 0) +
+        (data.cleared ? " · 清库 " + data.cleared : "") +
         " · 左拖加载更多 · 后台 " +
         (data.chart_poll_interval_sec || 5) +
         "s";