feat(task-watcher): watcher.py — 30초 loop + queue:paused 토글 (SP-10)

trading → SET queue:paused 1 EX 600 / free → DEL.
holidays 1시간마다 refresh. PAUSED_TTL 600s (watcher 죽어도 자동 해제 — 안전).
mode 전환 시에만 로그.
Plan-B-Infra Phase 2.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

services/task-watcher/watcher.py

@@ -0,0 +1,59 @@
+"""30초마다 current_mode 판정 → queue:paused 토글.
+
+trading → SET queue:paused 1 EX 600 (10분 TTL — watcher 죽어도 자동 해제)
+free    → DEL queue:paused
+holidays는 1시간마다 refresh (매 loop fetch 부하 회피).
+"""
+from __future__ import annotations
+
+import asyncio
+import datetime as dt
+import logging
+import os
+from zoneinfo import ZoneInfo
+
+import redis.asyncio as aioredis
+
+from mode import current_mode, fetch_holidays, KST
+
+logger = logging.getLogger(__name__)
+
+REDIS_URL = os.getenv("REDIS_URL", "redis://192.168.45.54:6379")
+PAUSED_KEY = "queue:paused"
+LOOP_INTERVAL = 30          # 초
+HOLIDAYS_REFRESH = 3600     # 1시간
+PAUSED_TTL = 600            # 10분 (watcher 죽어도 자동 해제)
+
+
+async def watcher_loop():
+    redis = aioredis.from_url(REDIS_URL, decode_responses=False)
+    holidays = fetch_holidays()
+    last_holiday_refresh = dt.datetime.now(KST)
+    last_mode = None
+    logger.info("task-watcher started (trading window 토글)")
+
+    while True:
+        try:
+            now = dt.datetime.now(KST)
+            # holidays 주기적 refresh
+            if (now - last_holiday_refresh).total_seconds() >= HOLIDAYS_REFRESH:
+                holidays = fetch_holidays()
+                last_holiday_refresh = now
+
+            mode = current_mode(now, holidays)
+            if mode == "trading":
+                await redis.set(PAUSED_KEY, b"1", ex=PAUSED_TTL)
+            else:
+                await redis.delete(PAUSED_KEY)
+
+            if mode != last_mode:
+                logger.info("mode 전환: %s → %s (paused=%s)", last_mode, mode, mode == "trading")
+                last_mode = mode
+
+            await asyncio.sleep(LOOP_INTERVAL)
+        except asyncio.CancelledError:
+            logger.info("watcher_loop cancelled")
+            raise
+        except Exception:
+            logger.exception("watcher_loop iteration 실패, 30초 후 재시도")
+            await asyncio.sleep(LOOP_INTERVAL)