refactor: worker_id 잔재 제거 - user_id 기반으로 완전 전환

- workerModel: remove()를 user_id 기반 cascading delete로 전환
- workerController: 계정 생성/해제를 workers.user_id 연결 방식으로 변경
- userController: JOIN 방향 전환 (u.worker_id→w.worker_id 에서 w.user_id→u.user_id)
- authController, systemController, authRoutes: 모든 CRUD에서 worker_id 참조 제거
- DB: UNIQUE KEY 5개 교체, FK 7개 삭제, daily_worker_summary user_id 추가

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

system1-factory/api/controllers/userController.js

@@ -43,7 +43,6 @@ const getAllUsers = asyncHandler(async (req, res) => {
         r.name as role,
         u._access_level_old as access_level,
         u.is_active,
-        u.worker_id,
         w.worker_name,
         w.department_id,
         d.department_name,
@@ -52,7 +51,7 @@ const getAllUsers = asyncHandler(async (req, res) => {
         u.last_login_at as last_login
       FROM users u
       LEFT JOIN roles r ON u.role_id = r.id
-      LEFT JOIN workers w ON u.worker_id = w.worker_id
+      LEFT JOIN workers w ON w.user_id = u.user_id
       LEFT JOIN departments d ON w.department_id = d.department_id
       ORDER BY u.created_at DESC
     `;
@@ -224,7 +223,7 @@ const updateUser = asyncHandler(async (req, res) => {
   checkAdminPermission(req.user);
 
   const { id } = req.params;
-  const { username, name, email, role, role_id, password, worker_id } = req.body;
+  const { username, name, email, role, role_id, password } = req.body;
 
   if (!id || isNaN(id)) {
     throw new ValidationError('유효하지 않은 사용자 ID입니다');
@@ -233,7 +232,7 @@ const updateUser = asyncHandler(async (req, res) => {
   logger.info('사용자 수정 요청', { userId: id, body: req.body });
 
   // 최소 하나의 수정 필드가 필요
-  if (!username && !name && email === undefined && !role && !role_id && !password && worker_id === undefined) {
+  if (!username && !name && email === undefined && !role && !role_id && !password) {
     throw new ValidationError('수정할 필드가 없습니다');
   }
 
@@ -324,22 +323,6 @@ const updateUser = asyncHandler(async (req, res) => {
       values.push(hashedPassword);
     }
 
-    // worker_id 업데이트 (null도 허용 - 연결 해제)
-    if (worker_id !== undefined) {
-      if (worker_id !== null) {
-        // worker_id가 유효한지 확인
-        const [workerCheck] = await db.execute('SELECT worker_id, worker_name FROM workers WHERE worker_id = ?', [worker_id]);
-        if (workerCheck.length === 0) {
-          throw new ValidationError('유효하지 않은 작업자 ID입니다');
-        }
-        logger.info('작업자 연결', { userId: id, worker_id, worker_name: workerCheck[0].worker_name });
-      } else {
-        logger.info('작업자 연결 해제', { userId: id });
-      }
-      updates.push('worker_id = ?');
-      values.push(worker_id);
-    }
-
     updates.push('updated_at = NOW()');
     values.push(id);