Enhancement request: add warning for older dm+d codelists

Summary

Add warning for users cloning older dm+d codelists:

User joined Office Hours last week and asked why he couldn't edit the clone of a dm+d codelist. It turns out that the codelist is so old that the dm+d builder is unable to handle it and so the user will need to create it from scratch unfortunately.

What would you like to achieve?

Make it clear to users that dm+d codelists (or does this apply to other codelist systems?) beyond a certain age won't be editable after cloning and would need to be recreated instead.

Who would benefit and how?

Users find the cloning feature useful to update codelists that were created by another user. But it's off-putting if they don't know that some codelists can't be edited after using the new feature.
It's makes sense that the older codelists may not be easily editable but users may not be aware of this or why. Some messaging would help dispel the feeling they're missing something / done something wrong.

Trace the codelist cloning flow and identify how dm+d codelist age and editability are determined. Confirm the age threshold and whether the same limitation applies to other codelist systems. Done means users receive clear messaging that an old cloned codelist cannot be edited and must be recreated instead.