Add next_cursor to OA approval list result for pagination

[Copilot]

OaApi.GetApprovalInfo request already supports cursor, but the response model lacked next_cursor, making documented pagination flow unusable from SDK types. This change exposes the response cursor so callers can iterate pages safely.

• Model update: OA approval list response

  • Added next_cursor to GetApprovalInfoResult (OAJson/GetApprovalInfoResult.cs).
  • Keeps wire format aligned with WeCom OA API pagination contract.

• Contract coverage: deserialization

  • Added GetApprovalInfoResultSupportsPaginationCursor in ApprovalContractTests.
  • Verifies sp_no_list and next_cursor deserialize together from API JSON.

• Usage (pagination loop)

  var req = new GetApprovalInfoRequest { starttime = "...", endtime = "...", cursor = 0, size = 100 };
  GetApprovalInfoResult page;
  do
  {
      page = OaApi.GetApprovalInfo(accessToken, req);
      // consume page.sp_no_list
      req.cursor = page.next_cursor;
  } while (page.sp_no_list != null && page.sp_no_list.Count > 0);

• Fixes 能循环获取审批单号吗？ #3326

[JeffreySu]

@copilot can you show me the official document URL and primary content. And you have to check the property name again.

[JeffreySu]

@copilot Your solution is wrong!