Return proof post content in Query API response

[nykma]

GET /v1/proof should returns the last fetched proof post content (with signature payload) to let user validate it.

[tanyas-codes]

@nykma Hello,I would want to contribute to this repo as a part of OSPP-2024,how do i get started?

[nykma]

@tanyas-codes
Sorry but we havn't attend this year's OSPP.
We still welcomes any contribution though. Thanks for your attention to our project!