The undated bucket count was page-local — derived from the year-grouping
of the current page's items, so it could never exceed the page size. The
owner's decision is for it to reflect ALL undated documents matching the
active filter across every page.
Add an undatedCount field to DocumentSearchResult, computed once per search
via a COUNT over the same filter spec with undatedOnly(true) forced —
independent of the "Nur undatierte" toggle so it never collapses to the
page slice or double-counts. A from/to range excludes undated rows by the
collision rule, so the count is legitimately 0 inside a date range.
Refs #668
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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