Fixes a critical bug in FTS query building where multi-word searches
with field restrictions incorrectly used OR between all word+field
combinations instead of requiring ALL words to match within at least
one field.
Example: searching "cute cat" in {title, tags} previously produced:
title:cute* OR title:cat* OR tags:cute* OR tags:cat*
Which matched recipes with ANY word in ANY field.
Now produces:
(title:cute* title:cat*) OR (tags:cute* tags:cat*)
Which requires ALL words to match within at least one field.
Also adds fallback to fuzzy search when FTS returns empty results,
improving search reliability.
Co-Authored-By: Claude <noreply@anthropic.com>
Introduce a new RecipeFTSIndex class that provides fast prefix-based search across recipe fields (title, tags, LoRA names/models, prompts) using SQLite's FTS5 extension. The implementation supports sub-100ms search times for large datasets (20k+ recipes) and includes asynchronous indexing, incremental updates, and comprehensive unit tests.
