Do you imagine this similar to CDK or Nutshell where you can provide a storage interface and if you don't, it uses a default db in the background (say indexdb when mobile, salute when node, etc?).
Discussion
in general yes, not sure about having a default though. potentially a wrapper around the existing cashu-ts api that adds storage functionality while keeping the core functions the same and accessible
my experience has been that proof management is the most bug prone aspect of a wallet... storing duplicate proofs, deleting proofs before a melt is confirmed, keeping spent proofs, not getting the change, etc.
also managing things like unpaid mint quotes is cumbersome