feat: replace volatility breakout with DB-backed real-time trend check

- price_history table on Oracle ADB stores prices every 10 minutes
- check_trend(): current price vs N hours ago (default 1h, +3% threshold)
- check_momentum(): unchanged (MA20 + 2x volume still applies)
- Ticker list cached 5 minutes to avoid 429 rate limits
- Collector starts 30s after boot to avoid simultaneous API calls
- Configurable: TREND_HOURS, TREND_MIN_GAIN_PCT in .env

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

core/market.py

@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 import logging
+import time
 
 import pyupbit
 import requests
@@ -12,9 +13,17 @@ logger = logging.getLogger(__name__)
 TOP_N = 20  # 거래량 상위 N개 종목만 스캔
 _TICKER_URL = "https://api.upbit.com/v1/ticker"
 
+# 티커 목록 캐시 (5분 TTL — API rate limit 방지)
+_ticker_cache: list[str] = []
+_ticker_cache_time: float = 0.0
+_TICKER_CACHE_TTL = 300  # 5분
+
 
 def get_top_tickers() -> list[str]:
-    """24시간 거래대금 상위 KRW 마켓 티커 반환."""
+    """24시간 거래대금 상위 KRW 마켓 티커 반환 (5분 캐시)."""
+    global _ticker_cache, _ticker_cache_time
+    if _ticker_cache and (time.time() - _ticker_cache_time) < _TICKER_CACHE_TTL:
+        return _ticker_cache
     try:
         all_tickers = pyupbit.get_tickers(fiat="KRW")
         if not all_tickers:
@@ -37,11 +46,13 @@ def get_top_tickers() -> list[str]:
         # 24h 거래대금 기준 정렬
         ticker_data.sort(key=lambda x: x.get("acc_trade_price_24h", 0), reverse=True)
         top = [t["market"] for t in ticker_data[:TOP_N]]
+        _ticker_cache = top
+        _ticker_cache_time = time.time()
         logger.debug(f"상위 {TOP_N}개: {top[:5]}...")
         return top
     except Exception as e:
         logger.error(f"get_top_tickers 실패: {e}")
-        return []
+        return _ticker_cache  # 실패 시 이전 캐시 반환
 
 
 def get_ohlcv(ticker: str, count: int = 21):