feat: add Telegram notifications and configurable stop loss

- notify.py: buy/sell/error alerts via upbit_trading_jm_bot
- STOP_LOSS_PCT: trailing stop configurable via .env (default -5%)
- notify_buy/notify_sell called on every trade execution

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

core/monitor.py

@@ -10,7 +10,7 @@ from . import trader
 
 logger = logging.getLogger(__name__)
 
-STOP_LOSS_PCT = 0.10        # 최고가 대비 -10% → 트레일링 스탑
+STOP_LOSS_PCT = float(os.getenv("STOP_LOSS_PCT", "5")) / 100  # 최고가 대비 -N% → 트레일링 스탑
 CHECK_INTERVAL = 10         # 10초마다 체크
 
 # 타임 스탑: N시간 경과 후 수익률이 M% 미만이면 청산