- Add tags_filter parameter to SearchMediaItemsUnified
- Add EXISTS clause with word_similarity() for fuzzy tag matching
- Add tag similarity scoring to ORDER BY clause (GREATEST function)
- Add SearchTagsValues query for autocomplete with ::TEXT cast
- Keep genre_filter for backward compatibility
- Regenerate Go code with sqlc generate
This enables filtering books by tags (from Calibre) instead of genre,
which is always NULL for imported books. Uses fuzzy matching consistent
with author/series filters, with best matches sorted first.
Relates to IMPLEMENTATION_TAGS_FILTER.md Phase 1