Remove local proto/, buf.yaml, buf.gen.yaml, and generated internal/api/v1/*.pb.go. The message-plane contract now lives in the sibling repo kmsvc-proto (forgejo.riotpiao.homelab.com/rock/kmsvc-proto), fetched via go get — no local buf/protoc plugin install needed. Nothing in this repo imported internal/api/v1 yet, so this is a clean swap with no call-site changes.