Refactor node storage and use proper types for protocol data

- Rename TypeID to ID throughout
- Remove re-derivable data (MACTableSize, SACNInputs now derived)
- Use typed ArtNetUniverse and SACNUniverse with methods
- Store multicast groups with lastSeen tracking in structs
- Remove int indexes in Nodes, use direct node pointers
- Parse multicast groups into typed struct instead of strings

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

ping.go

@@ -142,7 +142,7 @@ func (t *Tendrils) pingNode(node *Node) {
 	t.nodes.mu.RLock()
 	var ips []string
 	nodeName := node.DisplayName()
-	nodeID := node.TypeID
+	nodeID := node.ID
 	for _, iface := range node.Interfaces {
 		for ipStr := range iface.IPs {
 			ip := net.ParseIP(ipStr)