Add /queue/next endpoint and bump version

Introduce a new GET /queue/next endpoint (app/api/queue/routes/next.py) that returns the most recently updated queue record, optionally filtered by collection and group. Register the new router in app/api/queue/__init__.py and bump package version to 2.2.6. Also add a Postman collection (Python°.postman_collection.json) for local API testing.

Author: goldlabelapps