feat(grpc): add earliest/latest block height to GetSyncing response

Extend the GetSyncingResponse in cosmos.base.tendermint.v1beta1.Service
to include earliest_block_height and latest_block_height fields.

This enables gRPC clients (like indexers) to discover block availability
without needing to query the CometBFT RPC separately. The fields expose
the same information as the /status RPC endpoint's sync_info.

Changes:
- Add earliest_block_height field to GetSyncingResponse proto
- Add latest_block_height field to GetSyncingResponse proto
- Update service implementation to populate new fields from SyncInfo

Author: Cordtus

client/grpc/cmtservice/query.pb.go

@@ -55,7 +55,9 @@ func (s queryServer) GetSyncing(ctx context.Context, _ *GetSyncingRequest) (*Get
 	}
 
 	return &GetSyncingResponse{
-		Syncing: status.SyncInfo.CatchingUp,
+		Syncing:             status.SyncInfo.CatchingUp,
+		EarliestBlockHeight: status.SyncInfo.EarliestBlockHeight,
+		LatestBlockHeight:   status.SyncInfo.LatestBlockHeight,
 	}, nil
 }
 

client/grpc/cmtservice/service.go

@@ -126,6 +126,10 @@ message GetSyncingRequest {}
 // GetSyncingResponse is the response type for the Query/GetSyncing RPC method.
 message GetSyncingResponse {
   bool syncing = 1;
+  // earliest_block_height is the earliest block height available on this node.
+  int64 earliest_block_height = 2;
+  // latest_block_height is the latest block height available on this node.
+  int64 latest_block_height = 3;
 }
 
 // GetNodeInfoRequest is the request type for the Query/GetNodeInfo RPC method.