Alert API result-window check no longer applies to unfiltered page-0 requests

GET /alerts no longer returns HTTP 422 result_window_exceeded for an
unfiltered page-0 request just because your organization has more than
50,000 alerts. Integration connectivity checks and simple first-page reads are
served normally with the true metadata.count.

The 50,000-result boundary still applies in two cases:

• Pagination depth: a request whose page * page_size reaches 50,000
  returns 422 for any search.
• Time-windowed searches: a search filtered by last_activity_timestamp,
  last_activity_before, created_after, or created_before that matches
  more than 50,000 alerts returns 422 on page 0. Narrow the time range and
  retry.