fix(tksafety): DB 스키마 불일치로 인한 API 500 에러 수정

- departments.name → department_name (3곳)
- users → sso_users 테이블 참조 수정 (7곳)
- tbm_sessions.start_time → created_at (존재하지 않는 컬럼)
- tbm_team_assignments JOIN: ta.user_id → ta.worker_id
- workers leader JOIN: leader.worker_id → leader.user_id
- tbm_weather_conditions → weather_conditions 테이블명 수정

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

tksafety/api/models/checklistModel.js

@@ -46,7 +46,7 @@ async function deleteCheck(checkId) {
 // Get weather conditions
 async function getWeatherConditions() {
   const db = getPool();
-  const [rows] = await db.query('SELECT * FROM tbm_weather_conditions ORDER BY display_order, condition_code');
+  const [rows] = await db.query('SELECT * FROM weather_conditions ORDER BY display_order, condition_code');
   return rows;
 }