fix: support exporting and importing mfaInfo in auth

[VishalRaut2106]

Fixes auth:export and auth:import silently discarding MFA user data (mfaInfo) by explicitly including the 'mfaInfo' key in the allowed JSON extraction and validation fields.

Scenarios Tested

• JSON auth export correctly contains mfaInfo array (verified with unit tests).
• JSON auth import successfully parses and validates mfaInfo (verified with unit tests).

Sample Commands

firebase auth:export accounts.json --format=json
firebase auth:import accounts.json --hash-algo=scrypt --hash-key=xxx --salt-separator=xxx --rounds=8 --mem-cost=14

Fixes #10704

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[gemini-code-assist]

Code Review

This pull request resolves an issue where auth:export and auth:import dropped mfaInfo data for users with Multi-Factor Authentication enabled. This is fixed by adding mfaInfo to the exported and allowed JSON keys in both accountExporter.ts and accountImporter.ts, supported by new unit tests. The review feedback correctly points out a style guide violation where any[] is used for mfaInfo in the test file, and suggests defining a proper type structure instead.

[gemini-code-assist]

According to the repository style guide, we should never use any or unknown as an escape hatch. Please define a proper type/interface or inline the expected structure for mfaInfo instead of using any[].

      mfaInfo?: {
        mfaEnrollmentId: string;
        displayName?: string;
        phoneInfo?: string;
        enrolledAt?: string;
      }[];

References

1. Never use any or unknown as an escape hatch. Define proper interfaces/types or use type guards. ^(link)

[VishalRaut2106]

Fixed a missing semicolon on line 36 that was causing the global CI linter check to fail for the entire repository