nations worker: Street Soccer Pro weekly goals by country

POST /v1/sync takes a nations.v1.SyncRequest protobuf body (proto/nations.proto), Content-Type application/x-protobuf,
Authorization: Bearer INGEST_TOKEN. It adds each week's counts once per batch id and answers a SyncResponse with the
top rows of the asked week; result 0 = added or nothing to add, 1 = batch seen before, nothing added again.
400 malformed, 401 auth, 5xx failure, as plain text. X-Body-Encoding: base64 carries both bodies as base64 text.