Generate and ask user to copy backup codes when TOTP based 2FA is enabled

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Is your feature request related to a problem? Please describe.

• Backup codes is a section below the TOTP (Authenticator App) setting
• This means it is an optional thing that users can select
• So many users don't actually generate backup codes and then lose access to their account

Describe the solution you'd like

• Clear call to action to generate 2FA backup codes whenever 2FA is enabled
• For e.g. proton account settings give a modal like:

Describe alternatives you've considered

• Maybe some text in bold asking user to generate backup codes without fail could be a "quick win" solution

Additional context

No implementation files or tests are named. Start by locating the TOTP setting and existing backup-code section in the Nextcloud Server UI, then trace what happens when 2FA is enabled. Done should include a clear prompt to generate and copy backup codes without removing the existing backup-code option.