Replace the ~29 repeated `new SearchFilters(null, null, null, null, null,
null, null, null, null, false)` literals across the search test suites with
a shared SearchFiltersFixtures.noFilters() factory (and noFilters()
.withUndated(true) for the undated-only case). Tests that pin a specific
field keep their explicit `new SearchFilters(...)` so intent stays visible.
Pure test-ergonomics cleanup raised in the #702 review; no behaviour change.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>