/api/search pagination.total reports the page window, not the true match count

[dubadub]

Problem

SearchIndex::search (src/indexer/search.rs) computes the total match count from the already-truncated result set:

let top_docs = searcher
    .search(&*tantivy_query, &TopDocs::with_limit(limit + offset))?;

// Get total count
let total = top_docs.len();

TopDocs::with_limit(limit + offset) caps the collector at the current page window, so top_docs.len() saturates at limit + offset rather than counting all matching documents.

Effect

• total and total_pages are wrong for any query matching more documents than one page holds.
• It grows as you paginate deeper, which reads as a moving target: ?page=5&limit=100 reports total: 500 regardless of how many recipes actually match.
• total_pages (total.div_ceil(limit)) is derived from it, so pagination controls in the web UI are wrong too.

Reproduce:

curl -s 'http://localhost:3000/api/search?q=&limit=100&page=1' | jq .pagination   # total: 100
curl -s 'http://localhost:3000/api/search?q=&limit=100&page=5' | jq .pagination   # total: 500

Suggested fix

Use Tantivy's Count collector for the true total, alongside TopDocs for the page:

use tantivy::collector::{Count, TopDocs};

let (top_docs, total) = searcher.search(
    &*tantivy_query,
    &(TopDocs::with_limit(limit + offset), Count),
)?;

Count scores nothing and just counts matches, so the extra cost is small.

Context

Found during end-to-end verification of recipe locale detection (#11). Pre-existing and unrelated to locale — left out of scope there.