Rename MFA to 2FA

2FA (Two-factor authentication) is a subset of MFA (multi-factor authentication) but we'd like to update the app because:

1. At the time of writing, we only support 2 factors, not 2+ factors.
2. The term "MFA" is seemingly only the norm in very high security/sensitivity applications. While OpenFn is used in this context, we think a term like "2FA" will be more recognizable to our users, thus encouraging them to use it more frequently! (Right now there are 14M hits for "multi-factor authentication" and 26M hits for "two-factor authentication".) Even if this makes us look less secure, it will probably make our community actually be more secure.

Notes:

• That will require database column changes.
• Search for both "MFA" and "multi-factor authentication" and replace with "2FA" and "two-factor authentication".
• I've added a label "question" to this card because if/when we support a 3rd factor, we will presumably have to change everything back. This feels unlikely in the short term, but I'm still hesitant because of the required database changes. Thoughts?

Start with a repository-wide search for “MFA” and “multi-factor authentication”, then inspect the database schema and migrations for the columns that require renaming. Confirm the terminology and database changes are acceptable before proceeding; done means the application consistently uses “2FA” and “two-factor authentication” without breaking existing data or references.