feat: [로그인] 사용자 정보에 department_id 추가 반환

- getUserInfoForLogin에서 department_id도 함께 반환

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

app/Services/MemberService.php

@@ -231,6 +231,7 @@ public static function getUserInfoForLogin(int $userId): array
             $dept = DB::table('departments')->where('id', $profile->department_id)->first();
             if ($dept) {
                 $userInfo['department'] = $dept->name;
+                $userInfo['department_id'] = $dept->id;
             }
         }