When many ZIMs are already installed locally, a single Kiwix catalog page
(12 items) could return 12 already-installed items, which zim_service
would fully filter out client-side. The endpoint returned items: [] with
has_more: true, and the frontend's infinite-scroll guard
(flatData.length > 0) blocked fetchNextPage — leaving the user with
"No records found" despite plenty of uninstalled ZIMs available.
Backend now accumulates across up to 5 Kiwix fetches (60 items each)
until it has enough post-filter results to return, dedupes by entry id,
advances currentStart by actual entries returned (not requested), and
returns a next_start cursor. The frontend consumes that cursor instead
of computing Kiwix offsets locally, and the flatData.length > 0 guard is
removed so the existing on-mount effect drives bounded auto-fetch when
a short page lands.
The pre-existing has_more off-by-one (compared totalResults against the
input start rather than the post-fetch position) is fixed implicitly.
Diagnosis credit: @johno10661.
Closes#731
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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