Feishu → ZKTeco sync worker
  GET /preview                       — dry run, depts + users (add ?users=0 to skip users)
  GET /sync                          — full sync (depts + users)
  GET /sync-users                    — sync users only
  GET /test-person?empno=            — single-employee partial-update diff test
  GET /test-dept-users?name=…        — test one department’s users (add &dry=1 for preview)
  GET /test-dept-users?openid=…      — same, by open_department_id
  cron: 0 * * * *                    — auto full sync hourly