The unmatched-items search filtered only the current page's rows client-side.
Push the query server-side: HandleListUnmatchedItems takes an optional 'q' param
and filters title/library/type/status with parameterized ILIKE across all rows,
paginating the filtered set. Frontend hook takes a debounced search, resets to
page 1 on change, keeps the section mounted while searching. Also fixes stale
test mocks that returned the pre-pagination array shape instead of {items,total}.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
