feat(ai_trade): NAS Redis heartbeat (trader market_open/closed)

- ai_trade/heartbeat.py: build_trader_payload() + heartbeat_loop() 자체 미니 헬퍼
  (Windows 호스트 실행이라 _shared import 경로 달라 독립 구현, 계약은 동일)
- ai_trade/main.py: lifespan에 hb_task spawn + shutdown 시 cancel
  state_fn = scheduler._is_market_day & _is_polling_window(KST now) 조합
  signals = len(state.signals) 실시간 주입
- requirements.txt: redis>=5.0 추가
- ai_trade/tests/test_heartbeat.py: build_trader_payload 3케이스 TDD 검증

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019LV86jBozkNhSFXJA412fq

ai_trade/main.py

@@ -3,9 +3,12 @@ from __future__ import annotations
 import asyncio
 import logging
 from contextlib import asynccontextmanager
+from datetime import datetime
+from zoneinfo import ZoneInfo
 
 from fastapi import FastAPI
 
+from ai_trade import heartbeat as _hb
 from ai_trade import state as state_mod
 from ai_trade.chronos_predictor import ChronosPredictor
 from ai_trade.config import get_settings
@@ -13,8 +16,11 @@ from ai_trade.kis_client import KISClient
 from ai_trade.kis_websocket import KISWebSocket
 from ai_trade.pull_worker import poll_loop, make_asking_price_callback
 from ai_trade.rate_limit import SignalDedup
+from ai_trade.scheduler import _is_polling_window, _is_market_day
 from ai_trade.stock_client import StockClient
 
+_KST = ZoneInfo("Asia/Seoul")
+
 logger = logging.getLogger(__name__)
 
 
@@ -23,6 +29,7 @@ class AppContext:
     dedup: SignalDedup | None = None
     shutdown: asyncio.Event | None = None
     poll_task: asyncio.Task | None = None
+    hb_task: asyncio.Task | None = None
     kis_client: KISClient | None = None
     kis_ws: KISWebSocket | None = None
     chronos: ChronosPredictor | None = None
@@ -87,9 +94,27 @@ async def lifespan(app: FastAPI):
         )
     )
 
+    def _trader_state() -> tuple[str, int]:
+        """scheduler의 실제 폴링 윈도우 판정으로 market_open/market_closed 결정."""
+        now = datetime.now(_KST)
+        is_open = _is_market_day(now) and _is_polling_window(now)
+        state_str = "market_open" if is_open else "market_closed"
+        signals = len(state_mod.state.signals)
+        return state_str, signals
+
+    _ctx.hb_task = asyncio.create_task(_hb.heartbeat_loop(_trader_state))
+
     yield
 
-    # Shutdown
+    # Shutdown heartbeat task
+    if _ctx.hb_task is not None:
+        _ctx.hb_task.cancel()
+        try:
+            await _ctx.hb_task
+        except asyncio.CancelledError:
+            pass
+
+    # Shutdown poll task
     if _ctx.shutdown is not None:
         _ctx.shutdown.set()
     if _ctx.poll_task is not None: