refactor: add phone reauthentication and move reauth UI logic out of AuthService

[russellwheatley]

Key Changes:

• Removed passwordPrompt and EmailProvider from AuthService - Eliminated internal password prompting logic, delegating UI presentation to the view layer as it should be. Keep UI logic out of the AuthService.
• Implemented Phone Auth reauthentication, previously it was throwing an error, but now we handle it by throwing the below noted phoneReauthenticationRequired error with phone number which kickstarts phone reauth.
• Structured Reauthentication Errors - Introduced three specific error types that include actionable context:

emailReauthenticationRequired(context: EmailReauthContext) - includes user's email address
phoneReauthenticationRequired(context: PhoneReauthContext) - includes user's phone number
oauthReauthenticationRequired(context: OAuthReauthContext) - includes provider ID and display name

• New OAuth Reauthentication Method - Added reauthenticate(context:) that automatically locates registered OAuth providers (Google, Apple, Facebook, Twitter, etc.), obtains fresh credentials, and completes reauthentication without manual credential management.
• Created another reauthenticate(credential:) for when email/password create a credential for reauth.
• View-Layer Reauthentication Handling for default Views - Introduced ReauthenticationCoordinator and ReauthenticationModifier to manage reauthentication UI flows declaratively. The coordinator presents appropriate UI (alerts, sheets, password prompts, SMS verification) based on the error context type.
• Helper Function - Added withReauthenticationIfNeeded() that wraps operations requiring reauthentication, automatically catching reauth errors, presenting UI, and retrying the operation after successful reauthentication.

OAuth provider reauthentication

Simulator.Screen.Recording.-.iPhone.17.Pro.-.2025-11-18.at.16.07.54.mov

Email provider reauthentication

Simulator.Screen.Recording.-.iPhone.17.Pro.-.2025-11-18.at.16.28.24.mov

Phone provider reauthentication

Unfortunately, I hit the phone number sign-in limit so I've taken screenshots of the flow: