feat(api): add v2 sandbox contracts (#4716)

## Summary

adds rest v2 protobuf contracts for the sandbox apis so they can be used
by cloud with the grpc gateway and exposed to the cli. excludes these
from the dev server mcp catalog.

monorep side is [here](https://github.com/inngest/monorepo/pull/8150).
<- see there for using the cli locally.