[n7studios]

Summary

Fixes testFilterSubscribersPagination, which now fails consistently.

After paging forward with after_cursor and then back with before_cursor, the test asserted has_previous_page: true and has_next_page: false on page 1. The /v4/subscribers/filter endpoint now correctly returns has_previous_page: false and has_next_page: true. That matches GET /v4/subscribers and every other pagination test.

This is an API-side behaviour change. The assertions are unchanged since filter_subscribers() was added and used to pass.

Testing

Existing tests pass.

Checklist

• I have written a test and included it in this PR
• I have run all tests and they pass
• The code passes when running the PHP CodeSniffer
• The code passes when running PHPStan
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