1) Userless orders will be merged on user's registration by their phone number and/or email. Added Viewset action "merge_recently_viewed" so recently viewed products may be stored on server's side.
2) Added comprehensive products' filtering by category(support for including subcategories)
Fixes: I18N
Fixes: 1) Adjust import order in `core/models.py` for better consistency;
Extra: Refactor formatting for better readability in `core/models.py`; Update `pyproject.toml` version to 2.6.2; Update compiled translation file `cs_CZ/LC_MESSAGES/django.mo`.
