graph/db: expose version in maybeCreateShellNode

Add a version parameter to maybeCreateShellNode to allow callers to
specify which gossip protocol version should be used when creating
shell nodes. Currently all callers pass GossipVersion1, but this
change sets up the foundation for v2 support.

Shell nodes are lightweight node entries containing only a protocol
version and public key, created before full node information is
available.

graph/db/sql_store.go

@@ -4239,14 +4239,20 @@ func marshalExtraOpaqueData(data []byte) (map[uint64][]byte, error) {
 func insertChannel(ctx context.Context, db SQLQueries,
 	edge *models.ChannelEdgeInfo) error {
 
+	v := lnwire.GossipVersion1
+
 	// Make sure that at least a "shell" entry for each node is present in
 	// the nodes table.
-	node1DBID, err := maybeCreateShellNode(ctx, db, edge.NodeKey1Bytes)
+	node1DBID, err := maybeCreateShellNode(
+		ctx, db, v, edge.NodeKey1Bytes,
+	)
 	if err != nil {
 		return fmt.Errorf("unable to create shell node: %w", err)
 	}
 
-	node2DBID, err := maybeCreateShellNode(ctx, db, edge.NodeKey2Bytes)
+	node2DBID, err := maybeCreateShellNode(
+		ctx, db, v, edge.NodeKey2Bytes,
+	)
 	if err != nil {
 		return fmt.Errorf("unable to create shell node: %w", err)
 	}
@@ -4257,7 +4263,7 @@ func insertChannel(ctx context.Context, db SQLQueries,
 	}
 
 	createParams := sqlc.CreateChannelParams{
-		Version:     int16(lnwire.GossipVersion1),
+		Version:     int16(v),
 		Scid:        channelIDToBytes(edge.ChannelID),
 		NodeID1:     node1DBID,
 		NodeID2:     node2DBID,
@@ -4326,12 +4332,12 @@ func insertChannel(ctx context.Context, db SQLQueries,
 // created. The ID of the node is returned. A shell node only has a protocol
 // version and public key persisted.
 func maybeCreateShellNode(ctx context.Context, db SQLQueries,
-	pubKey route.Vertex) (int64, error) {
+	v lnwire.GossipVersion, pubKey route.Vertex) (int64, error) {
 
 	dbNode, err := db.GetNodeByPubKey(
 		ctx, sqlc.GetNodeByPubKeyParams{
 			PubKey:  pubKey[:],
-			Version: int16(lnwire.GossipVersion1),
+			Version: int16(v),
 		},
 	)
 	// The node exists. Return the ID.
@@ -4344,7 +4350,7 @@ func maybeCreateShellNode(ctx context.Context, db SQLQueries,
 	// Otherwise, the node does not exist, so we create a shell entry for
 	// it.
 	id, err := db.UpsertNode(ctx, sqlc.UpsertNodeParams{
-		Version: int16(lnwire.GossipVersion1),
+		Version: int16(v),
 		PubKey:  pubKey[:],
 	})
 	if err != nil {