Fix django-allauth deprecation warnings

[hugovk]

Description

• Fix django-allauth deprecation warnings shown during make serve, make test, and so on.

Before

❯ make test
docker compose run --rm web ./manage.py test
[+] Creating 2/0
 ✔ Container pythondotorg-redis-1     Running                                                                            0.0s
 ✔ Container pythondotorg-postgres-1  Running                                                                            0.0s
Found 661 test(s).
Creating test database for alias 'default'...
System check identified some issues:

WARNINGS:
?: settings.ACCOUNT_AUTHENTICATION_METHOD is deprecated, use: settings.ACCOUNT_LOGIN_METHODS = {'username', 'email'}
?: settings.ACCOUNT_EMAIL_REQUIRED is deprecated, use: settings.ACCOUNT_SIGNUP_FIELDS = ['email*', 'username*', 'password1*', 'password2*']

System check identified 2 issues (0 silenced).
....................................................................

After

❯ make test
docker compose run --rm web ./manage.py test
[+] Creating 2/0
 ✔ Container pythondotorg-redis-1     Running                                                                            0.0s
 ✔ Container pythondotorg-postgres-1  Running                                                                            0.0s
Found 661 test(s).
Creating test database for alias 'default'...
System check identified no issues (0 silenced).
.......................................................

[Copilot]

Pull request overview

This pull request updates the django-allauth configuration to use the modern settings API, eliminating deprecation warnings that appeared during make serve and make test operations.

Changes:

• Replaced deprecated ACCOUNT_AUTHENTICATION_METHOD with ACCOUNT_LOGIN_METHODS
• Replaced deprecated ACCOUNT_EMAIL_REQUIRED with ACCOUNT_SIGNUP_FIELDS

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