visual enhancements of sifrovacka and stage page

requirements.txt

sifrovacka/migrations/0022_auto_20210905_1653.py

sifrovacka/migrations/0023_auto_20210905_1654.py

sifrovacka/migrations/0024_auto_20210905_1719.py

sifrovacka/migrations/0025_alter_stages_stage_urlhash.py

sifrovacka/migrations/0026_alter_stages_stage_urlhash.py

sifrovacka/models.py

sifrovacka/templates/sifrovacka.html

sifrovacka/templates/stage.html

sifrovacka/urls.py

sifrovacka/views.py