fix(dashboard): clean up stale position cache on unmatched close events

_handle_close was not clearing _current_positions when no matching OPEN
trade was found in DB, causing all subsequent entries for the same
symbol+direction to be silently skipped. Also add PYTHONUNBUFFERED=1
and python -u to make log parser crashes visible in docker logs.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

dashboard/api/log_parser.py

@@ -479,6 +479,7 @@ class LogParser:
 
         if not open_trades:
             print(f"[LogParser] 경고: {symbol} 청산 감지했으나 열린 포지션 없음")
+            self._current_positions.pop(symbol, None)
             return
 
         primary_id = open_trades[0]["id"]