add response types along with the shared zod schemas

[beniaminmunteanu]

The testnet frontends would benefit from having the response types of the backend APIs in a shared directory, so that they can be referenced instead of duplicated.

So the same way that we are sharing the zod schemas for request validations, we should also share the response types.

Suggestion: Maybe write them as interfaces, and have the backend Models also implement that interface

Controllers:

• [ ] wallet/account
• [ ] wallet/asset
• [ ] wallet/auth
• [ ] wallet/grant
• [ ] wallet/rapyd
• [ ] wallet/incomingPayment