fix(api): Remove redundant "totp" and "webauthn" fields from certain schemas

[PilkeySEK]

Summary

• What changed:
  • Added a AuthMfaMethod enum which has "totp" and "webauthn" as possible values
  • Modified the following schemas/interfaces/types:
    • LoginMfaResult in fluxer_api/src/api/auth/AuthLogin.ts
    • ResetPasswordResult in fluxer_api/src/api/auth/AuthPassword.ts
    • LoginMfaResponse and LoginResponse in fluxer_api/src/api/auth/tests/AuthTestUtils.ts
    • MfaLoginResponse in fluxer_app/src/features/auth/commands/AuthenticationCommands.ts
    • AuthMfaRequiredResponse in packages/schema/src/domains/auth/AuthSchemas.ts
• Why it is correct: The same information is already in allowed_methods , which lists totp and webauthn if they are available.
• Risk: I could have missed a location where this is missing (though unlikely because typescript would usually catch it).

Verification

• Tests run: Yes
• Manual checks: Registration and login worked just fine.
• Screenshots or recordings:

Checklist

• I understand every change in this PR.
• I can explain what it does and why it is correct.
• I disclosed any LLM coding help below.

LLM Disclosure

• None

[PilkeySEK]

(this might have backwards-compatibility problems because all clients would need to update at once, maybe)