[eileencodes]

This PR changes the following:

1. Ensures only mysql checks for safe migrations as postgresql and neki don't have safe migrations
2. Update the help to explain that MySQL is supported and Postgresql is only supported behind a feature flag. Neki isn't yet supported. 3) Include options in help for cluster size and replicas.

[cursor]

Cursor Bugbot has reviewed your changes using default effort and found 1 potential issue.

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[cursor]

Risk: medium. Approved. Cursor Bugbot’s check was skipped and Cursor Security Agent was not present; remaining signals and the medium-risk threshold allow approval. No reviewers were assigned.

  

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