document inventory sorting and test count

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

README.md

@@ -112,6 +112,10 @@ from scratch.
 - Catalog browsing works without an account; the catalog endpoints remain
   read-only.
 
+The inventory view can be filtered by category and searched by name/class
+name, and sorted by `name` (default), `category`, `quantity` (high to low) or
+`updated` (most recently changed first).
+
 Inventory rows store `(user_id, class_name, quantity, notes)`. Adding an item
 that is already present increments its quantity; quantity and notes can then be
 edited or the row removed. Responses are enriched live from the catalog. If a
@@ -157,7 +161,7 @@ curl -fsS -b cookies.txt http://localhost:8080/api/v1/me/inventory
 cd trade-hub/backend
 python3 -m venv .venv
 .venv/bin/pip install -r requirements.txt -r requirements-dev.txt
-.venv/bin/python -m pytest tests/ -q          # 45 tests, no database needed
+.venv/bin/python -m pytest tests/ -q          # 50 tests, no database needed
 DATA_DIR=./data/samples .venv/bin/uvicorn main:app --port 8000
 ```
 
@@ -186,7 +190,7 @@ POST   /api/v1/auth/login         {username, password}        -> 200 + session c
 POST   /api/v1/auth/logout                                    -> 204
 GET    /api/v1/auth/me                                        -> {user}
 
-GET    /api/v1/me/inventory?category=&search=&page=&page_size=
+GET    /api/v1/me/inventory?category=&search=&sort=&page=&page_size=
 GET    /api/v1/me/inventory/summary
 POST   /api/v1/me/inventory       {class_name, quantity?, notes?}
 PATCH  /api/v1/me/inventory/{class_name}   {quantity?, notes?}