fix: wechat account scrape (form-data+dates) + frontend staff page

Backend (scrape_wechat_accounts):
- Send wxUser/list as form-urlencoded (not JSON) with the REQUIRED filters
  isOnJob / departmentId / startdate / enddate + empty userId/salesname/
  weChatNickName, matching the live request (empty fails with code -90000).
- scrape_wechat_accounts now takes department_id (the company-root dept id)
  plus optional start/end defaulting to a recent 7-day UTC window.
- paginate_by_page gains a form=True mode (data= + form content-type).
- Orchestrator sync_wechat_accounts resolves the root dept from the
  Department table (or accepts one) and skips with a warning when unknown.
- seed_accounts.py resolves the root via scrape_departments.

Frontend (yunkes):
- Add StaffList.vue (/staff) with is_on_job filter + pagination.
- Add /staff route and a 员工 nav item between 客户 and 群.

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

yunke-server/tests/cassettes/wxUser_fixture.py

@@ -5,8 +5,15 @@ data dictionary §2: ``wechatId, nickName, alias, phone, userId,
 userName(员工真名), contactsNum, groupNum, sendNum/receiveNum, isOnJob,
 dbSize, 在线状态, lastUpdate``; total=55).
 
-The envelope differs from ``wxFriends/friend_list/es``: there is **no**
-``basicResult`` wrapper. The pagination fields sit directly under ``data``::
+The REQUEST is **form-urlencoded** (NOT JSON): the endpoint binds Spring
+``@RequestParam`` from the form body and REQUIRES ``isOnJob`` /
+``departmentId`` (the company-root dept id) / ``startdate`` / ``enddate`` or
+it answers ``code -90000`` ("缺少..."). ``userId`` / ``salesname`` /
+``weChatNickName`` are sent empty to mirror the real client.
+
+The RESPONSE envelope differs from ``wxFriends/friend_list/es``: there is
+**no** ``basicResult`` wrapper. The pagination fields sit directly under
+``data``::
 
     {"code":"10000","data":{"data":[...], "total":.., "pageNum":.., "pageSize":..}}