Fixes: 1) Correct router naming in `blog/urls.py` from `payment_router` to `blog_router` for clarity;
Extra: 1) Refactor obsolete `StaticPagesSitemap.PAGES` structure with a dynamic `items` method; 2) Create placeholder 404 URLs for non-existent slugs; 3) Update and simplify docstring for `Post` class, replacing inline details with a concise translation-aware docstring.