feat(api): GET /api/moments 朋友圈列表(desc分页+账号头部)

对齐云客员工聊天窗口朋友圈tab:帖子 create_time desc 分页 +
wechat_account 头部(昵称/头像/别名);员工不存在不404(header全None
前端兜底)。头像提取抽共享 helper account_avatar 放 organization.py,
accounts 列表与 moments 头部复用。

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

yunke-server/app/api/main.py

@@ -11,6 +11,7 @@ Includes:
 * ``GET /api/departments`` / ``/api/staff`` / ``/api/accounts``
   (see :mod:`app.api.routers.organization`).
 * ``GET /api/messages`` (see :mod:`app.api.routers.messages`).
+* ``GET /api/moments`` (see :mod:`app.api.routers.moments`).
 * ``GET /api/groups`` / ``/api/groups/{room_id}/members``
   (see :mod:`app.api.routers.groups`).
 * ``GET /api/calls`` (see :mod:`app.api.routers.calls`).
@@ -46,6 +47,7 @@ from app.api.routers import (
     groups,
     media,
     messages,
+    moments,
     organization,
     search,
     sessions,
@@ -81,6 +83,7 @@ app.include_router(customer.router)
 app.include_router(media.router)
 app.include_router(organization.router)
 app.include_router(messages.router)
+app.include_router(moments.router)
 app.include_router(groups.router)
 app.include_router(calls.router)
 app.include_router(sms.router)