NUT13-only Wallet with provided seed

[davidcaseria]

The Wallet will now only support NUT -13-based secret derivation. The cdk user must provide a seed, which is used to generate an internal Xpriv.

Also, the database counter is changed to a u32 since the maximum value is 2^31-1.

Closes #111
Closes #125
Relies on #126

[thesimplekid]

@davidcaseria Mind just rebaseing on main and squashing the commits? I can do it if not just let me know

[thesimplekid]

Thanks for the PR looks good. Think just remove the feature and good to go

[davidcaseria]

I simplified your suggestion to a one-liner: let count = count.map_or(0, |c| c + 1);. I think that's still pretty clear if you know what the map_or function does, but let me know if you'd like me to change it to your suggestion.

[thesimplekid]

I simplified your suggestion to a one-liner: let count = count.map_or(0, |c| c + 1);

Even better thanks