Fix (and reinstantiate phone login)

[ikusteu]

The phone login has is currently disabled. From the first look it seems as if the phone auth of fuirebaseui is incompatible with firebase v9 (the app object is expected to have property auth, which is the old way of doing things in firebase).

• [ ] Investigate firebaseui source code/releases/alternatives to confirm this theory
• [ ] Replace phone login with different implementation if necessary (and the issue is not resolved otherwise)

[ikusteu]

Closing this issue as new issue has been created for this #382