Makes the local search behave more like YouTube's — finding videos by the
uploader's own keywords or the query that surfaced them, not only words in the
title. A DB-generated, weighted search_vector (migration 0032) replaces the
title-only FTS index:
- keywords: the creator's snippet.tags (free — already in the snippet we fetch),
stored on enrich.
- search_terms: distinct live-search queries that surfaced the video (across all
users), appended by the search route — folds YouTube's relevance into local
search (a video YT returned for a query becomes findable by it even without a
title match), the user's own idea.
- description (truncated) for broad recall on the existing catalog.
Weighted title(A) > keywords+queries(B) > description(C) so ts_rank keeps title
hits on top. A plain GIN index on the generated column guarantees index use (no
expression/param matching). Verified on localdev: recall 146->213 for one query;
7 'eurovision' hits via the document but not the title; index scan confirmed.
