Topic naming (kmsvc.{queue}.shard-{id} / .fifo.shard-{id} / .dlq.shard-{id}), hash-range shard selection/splitting (murmur2-based, matching Kafka's default partitioner), and topic admin/producer/consumer client constructors shared by the operator and the message-plane.
Adds queue_service.proto (SendMessage, SendMessageBatch, ReceiveMessage, DeleteMessage, DeleteMessageBatch, ChangeMessageVisibility(Batch)) with grpc-gateway REST annotations, plus the generated Go server/client and gateway stubs.
Sets up go.mod/go.sum, buf (proto codegen) configuration, and the env-driven Config shared by the message-plane server and queue-operator.