Adds a self-referencing categories tree, a tag registry with
deterministic colours, and item_tags, plus admin CRUD for both.
GET /api/items now accepts category, tags, min_price and max_price.
Category matching walks the subtree with a recursive CTE so selecting a
parent includes everything filed beneath it; tags match with AND via a
count check, since ANY() alone would return items carrying only one of
them. Malformed filter params return 400 rather than being ignored, so a
broken link doesn't quietly list the whole catalogue.
GET /api/filters serves the drawer its tree, tags, and price bounds in
one request.
Item image/tag aggregation moves from LEFT JOIN + GROUP BY to scalar
subqueries. Joining two one-to-many relations multiplies their rows, so
an item with 2 images and 3 tags would have repeated every image three
times once tags were added.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>