P2: print→logging 전환, 포트폴리오 중복 제거, Docker healthcheck 추가

- backend/main.py: logging 모듈 도입, print() 제거
- stock-lab/main.py: print() → logger 전환, _calc_portfolio_totals 공용 함수 추출
- stock-lab/scraper.py: logging 모듈 도입, print() 제거
- docker-compose.yml: 전 서비스 healthcheck 블록 추가 (30s 간격, 3회 재시도)

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

backend/app/main.py

@@ -1,10 +1,14 @@
 import os
 import time
+import logging
 from typing import Optional, List, Dict, Any, Tuple
 from fastapi import FastAPI, HTTPException
 from pydantic import BaseModel
 from apscheduler.schedulers.background import BackgroundScheduler
 
+logging.basicConfig(level=logging.INFO, format="%(asctime)s [%(name)s] %(levelname)s %(message)s")
+logger = logging.getLogger("lotto-backend")
+
 from .db import (
     init_db, get_draw, get_latest_draw, get_all_draw_numbers,
     save_recommendation_dedup, list_recommendations_ex, delete_recommendation,
@@ -52,7 +56,7 @@ _PERF_CACHE_TTL = 3600  # 1시간 (스케줄러 미실행 상황 대비 폴백)
 def _refresh_perf_cache() -> None:
     _PERF_CACHE["data"] = get_recommendation_performance()
     _PERF_CACHE["at"] = time.time()
-    print("[PerfCache] 성과 통계 캐시 갱신")
+    logger.info("성과 통계 캐시 갱신")
 
 
 @app.on_event("startup")
@@ -86,7 +90,7 @@ def on_startup():
         target = latest["drw_no"] + 1
         report = generate_weekly_report(draws, target)
         save_weekly_report(target, _json.dumps(report, ensure_ascii=False))
-        print(f"[WeeklyReport] {target}회차 리포트 저장 완료")
+        logger.info(f"{target}회차 리포트 저장 완료")
 
     scheduler.add_job(_save_weekly_report_job, "cron", day_of_week="sat", hour=9, minute=0)