Full Russian locale — 389/389 English keys, Slavic plural forms, native Cyrillic. Rebased from PR #605 with rebase artifacts fixed. Login page Russian added to api/routes.py. Credits: @DrMaks22 (translation), @renheqiang (PR #605 author). Co-authored-by: DrMaks22 <DrMaks22@users.noreply.github.com> Co-authored-by: renheqiang <renheqiang@users.noreply.github.com>