Fixes: 1) Corrected `ForeignKey` type assertions across models; 2) Resolved typos and formatting inconsistencies in `.env` and README; 3) Fixed explicit boolean checks in user manager methods.
Extra: Updated type hints in multiple models, serializers, and views.
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
