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/authController.js

@@ -33,7 +33,7 @@ const login = asyncHandler(async (req, res) => {
 // ✅ 사용자 등록 기능 추가
 const register = async (req, res) => {
   try {
-    const { username, password, name, access_level, worker_id } = req.body;
+    const { username, password, name, access_level } = req.body;
     const db = await getDb();
 
     // 필수 필드 검증
@@ -72,9 +72,9 @@ const register = async (req, res) => {
 
     // 사용자 등록
     const [result] = await db.query(
-      `INSERT INTO users (username, password, name, role, access_level, worker_id) 
-       VALUES (?, ?, ?, ?, ?, ?)`,
-      [username, hashedPassword, name, role, access_level, worker_id]
+      `INSERT INTO users (username, password, name, role, access_level)
+       VALUES (?, ?, ?, ?, ?)`,
+      [username, hashedPassword, name, role, access_level]
     );
 
     console.log('[사용자 등록 성공]', username);
@@ -141,8 +141,8 @@ const getAllUsers = async (req, res) => {
 
     // 비밀번호 제외하고 조회
     const [rows] = await db.query(
-      `SELECT user_id, username, name, role, access_level, worker_id, created_at 
-       FROM users 
+      `SELECT user_id, username, name, role, access_level, created_at
+       FROM users
        ORDER BY created_at DESC`
     );