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/hub.py

@@ -675,6 +675,7 @@ def api_chart_ohlcv(
             bms = int(bms_raw)
         except ValueError:
             raise HTTPException(status_code=400, detail="before_ms 无效")
+    clear_db = force and not tail_refresh and bms is None
 
     def remote_fetch(**kwargs):
         tf_use = kwargs.get("timeframe") or timeframe
@@ -693,6 +694,7 @@ def api_chart_ohlcv(
         remote_fetch,
         force_refresh=force,
         tail_refresh=tail_refresh,
+        clear_db=clear_db,
         limit=lim,
         before_ms=bms,
     )