feat(tkuser): Sprint 001 Section A — 연차/휴가 백엔드 전환 (DB + API)

workers/vacation_balance_details → sso_users/sp_vacation_balances 기반 전환.
부서장 설정, 승인권한 CRUD, vacation_settings 테이블, 장기근속 자동부여,
startup migration 추가.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

user-management/api/index.js

@@ -17,6 +17,7 @@ const workplaceRoutes = require('./routes/workplaceRoutes');
 const equipmentRoutes = require('./routes/equipmentRoutes');
 const taskRoutes = require('./routes/taskRoutes');
 const vacationRoutes = require('./routes/vacationRoutes');
+const vacationSettingsRoutes = require('./routes/vacationSettingsRoutes');
 const partnerRoutes = require('./routes/partnerRoutes');
 const vendorRoutes = require('./routes/vendorRoutes');
 const consumableItemRoutes = require('./routes/consumableItemRoutes');
@@ -64,6 +65,7 @@ app.use('/api/workplaces', workplaceRoutes);
 app.use('/api/equipments', equipmentRoutes);
 app.use('/api/tasks', taskRoutes);
 app.use('/api/vacations', vacationRoutes);
+app.use('/api/vacation-settings', vacationSettingsRoutes);
 app.use('/api/partners', partnerRoutes);
 app.use('/api/vendors', vendorRoutes);
 app.use('/api/consumable-items', consumableItemRoutes);
@@ -85,9 +87,23 @@ app.use((err, req, res, next) => {
   });
 });
 
-app.listen(PORT, () => {
-  console.log(`tkuser-api running on port ${PORT}`);
-});
+// Startup: 마이그레이션 완료 후 서버 시작
+async function start() {
+  try {
+    const { runMigration } = require('./models/vacationSettingsModel');
+    await runMigration();
+  } catch (err) {
+    if (!['ER_DUP_FIELDNAME', 'ER_TABLE_EXISTS_ERROR', 'ER_DUP_KEYNAME'].includes(err.code)) {
+      console.error('Fatal migration error:', err.message);
+      process.exit(1);
+    }
+    console.error('Migration warning (ignored):', err.message);
+  }
+  app.listen(PORT, () => {
+    console.log(`tkuser-api running on port ${PORT}`);
+  });
+}
+start();
 
 // 오래된 알림 정리 cron (매일 03:00 KST)
 (function scheduleNotificationCleanup() {