feat: extract kafkamgmt.v1 proto contract from kafaka_management_service

Single source of truth for the wire contract shared by the server,
kmsvc-sdk, and kmsvc-cli. Ships proto source + buf lint/breaking-change
config only; consumers submodule this repo and codegen independently
with their own go_package override (see README.md).

.forgejo/workflows/ci.yaml

@@ -0,0 +1,22 @@
+name: ci
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  buf:
+    runs-on: docker
+    container:
+      image: bufbuild/buf:latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: buf lint
+        run: buf lint
+
+      - name: buf breaking (against main)
+        run: buf breaking --against '.git#branch=main'
+        if: github.ref != 'refs/heads/main'