Docker & Django - what directory does localhost point to?
This is most likely a problem with the django configuration better fitting to stackoverflow, and not so much a devops problem.

Check the settings.py for the following entries:

INSTALLED_APPS = [
    (...)
    'django.contrib.staticfiles',
]


At the end of this file

STATIC_ROOT='staticfiles'
STATIC_URL = '/static/'
STATICFILES_DIRS = [
     os.path.join(BASE_DIR, 'static'),
]


source Django manual: How to static-files