feat: initial upbit auto-trader implementation

Strategy C: volatility breakout (Larry Williams K=0.5) AND momentum
(MA20 + 2x volume surge) must both trigger for a buy signal.

Hard rules:
- Trailing stop: sell when price drops -10% from peak
- Max budget: 1,000,000 KRW total, up to 3 positions (333,333 KRW each)
- Scan top 20 KRW tickers by 24h trading volume every 60s
- Monitor positions every 10s

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

core/trader.py

@@ -0,0 +1,119 @@
+"""매수/매도 실행 및 포지션 관리."""
+
+from __future__ import annotations
+
+import logging
+import os
+import threading
+import time
+from typing import Optional
+
+import pyupbit
+from dotenv import load_dotenv
+
+load_dotenv()
+
+logger = logging.getLogger(__name__)
+
+MAX_BUDGET = 1_000_000       # 총 운용 한도: 100만원
+MAX_POSITIONS = 3            # 최대 동시 보유 종목 수
+PER_POSITION = MAX_BUDGET // MAX_POSITIONS  # 종목당 33만3천원
+
+_lock = threading.Lock()
+_positions: dict = {}
+# 구조: { ticker: { buy_price, peak_price, amount, invested_krw } }
+
+_upbit: Optional[pyupbit.Upbit] = None
+
+
+def _get_upbit() -> pyupbit.Upbit:
+    global _upbit
+    if _upbit is None:
+        _upbit = pyupbit.Upbit(os.getenv("ACCESS_KEY"), os.getenv("SECRET_KEY"))
+    return _upbit
+
+
+def get_positions() -> dict:
+    return _positions
+
+
+def buy(ticker: str) -> bool:
+    """시장가 매수. 예산·포지션 수 확인 후 진입."""
+    with _lock:
+        if ticker in _positions:
+            logger.debug(f"{ticker} 이미 보유 중")
+            return False
+
+        if len(_positions) >= MAX_POSITIONS:
+            logger.info(f"최대 포지션 도달({MAX_POSITIONS}), {ticker} 패스")
+            return False
+
+        invested = sum(p["invested_krw"] for p in _positions.values())
+        available = MAX_BUDGET - invested
+        order_krw = min(available, PER_POSITION)
+
+        if order_krw < 10_000:
+            logger.info(f"잔여 예산 부족({order_krw:,}원), {ticker} 패스")
+            return False
+
+        upbit = _get_upbit()
+        try:
+            current = pyupbit.get_current_price(ticker)
+            result = upbit.buy_market_order(ticker, order_krw)
+            if not result or "error" in str(result):
+                logger.error(f"매수 실패: {result}")
+                return False
+
+            time.sleep(0.5)  # 체결 대기
+            currency = ticker.split("-")[1]
+            amount = float(upbit.get_balance(currency) or 0)
+
+            _positions[ticker] = {
+                "buy_price": current,
+                "peak_price": current,
+                "amount": amount,
+                "invested_krw": order_krw,
+            }
+            logger.info(
+                f"[매수] {ticker} @ {current:,.0f}원 | "
+                f"수량={amount} | 투자금={order_krw:,}원"
+            )
+            return True
+        except Exception as e:
+            logger.error(f"매수 예외 {ticker}: {e}")
+            return False
+
+
+def sell(ticker: str, reason: str = "") -> bool:
+    """시장가 전량 매도."""
+    with _lock:
+        if ticker not in _positions:
+            return False
+
+        pos = _positions[ticker]
+        upbit = _get_upbit()
+        try:
+            result = upbit.sell_market_order(ticker, pos["amount"])
+            if not result or "error" in str(result):
+                logger.error(f"매도 실패: {result}")
+                return False
+
+            current = pyupbit.get_current_price(ticker)
+            pnl = (current - pos["buy_price"]) / pos["buy_price"] * 100
+            logger.info(
+                f"[매도] {ticker} @ {current:,.0f}원 | "
+                f"수익률={pnl:+.1f}% | 사유={reason}"
+            )
+            del _positions[ticker]
+            return True
+        except Exception as e:
+            logger.error(f"매도 예외 {ticker}: {e}")
+            return False
+
+
+def update_peak(ticker: str, current_price: float) -> None:
+    """최고가 갱신 (트레일링 스탑 기준선 상향)."""
+    with _lock:
+        if ticker in _positions:
+            if current_price > _positions[ticker]["peak_price"]:
+                _positions[ticker]["peak_price"] = current_price