refactor: 미사용 의존성 제거 + deprecated API 수정 + 정리

- SSO/System2: 미사용 redis, bcrypt, multer 의존성 제거
- System2: dbPool.js shim 삭제, workIssueModel을 config/database 직접 참조로 변경
- System3: deprecated datetime.utcnow() → datetime.now(timezone.utc)
- System3: deprecated @app.on_event("startup") → lifespan 패턴
- System3: 중복 /users 라우트 제거, 불필요 파일 삭제
- health-check.sh: tkuser API/Web 체크 추가
- tkuser nginx: upstream 이름 수정 (tk-system2-api → system2-api)

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

system3-nonconformance/api/services/auth_service.py

@@ -1,4 +1,4 @@
-from datetime import datetime, timedelta
+from datetime import datetime, timedelta, timezone
 from typing import Optional
 from jose import JWTError, jwt
 from passlib.context import CryptContext
@@ -48,9 +48,9 @@ def get_password_hash(password: str) -> str:
 def create_access_token(data: dict, expires_delta: Optional[timedelta] = None):
     to_encode = data.copy()
     if expires_delta:
-        expire = datetime.utcnow() + expires_delta
+        expire = datetime.now(timezone.utc) + expires_delta
     else:
-        expire = datetime.utcnow() + timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
+        expire = datetime.now(timezone.utc) + timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
     to_encode.update({"exp": expire})
     encoded_jwt = jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)
     return encoded_jwt