SSO providers directly displayed on the auth screen

What problem will this feature address?

The current implementation maps an email domain to a single SSO provider. This poses different problems:

• User has to type his email at every login => Friction for returning users
• User has a "blackbox" feeling : he can't predict what SSO provider his email will launch without knowing the list behind it.
• Admins cannot allow the use of multiple providers per email domain/per email adress

Describe the solution you'd like

For a new device:

Provider 1
Provider 2
...

Email
Password

For a returning user :

Last used provider
---
Provider 1
Provider 2
...

Email (prefilled with last auth email)
Password

/login/ URLs that directly start the SSO flow, for bookmarks and shortcuts use.

Describe alternatives you've considered

A remembering cookie for the sso email field, to keep it fast for sso users without fully implementing the "single-click SSO".

Additional context

• Jetbrains account login https://account.jetbrains.com/login
• GitLab login (from GNOME because they added custom providers) https://gitlab.gnome.org/users/sign_in

Will you send a PR to implement it?

No

No files, tests, or entry points are named. Start by locating the authentication screen and the existing email-domain SSO mapping, then trace how provider-specific login URLs are handled. Done means the screen can display available providers, preserve the returning user's last provider and email, and support direct provider URLs.