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>

http.go

@@ -230,7 +230,7 @@ func (t *Tendrils) getNodes() []*Node {
 	for _, node := range t.nodes.nodes {
 		n := new(Node)
 		*n = *node
-		n.Unreachable = unreachableNodes[node.TypeID]
+		n.Unreachable = unreachableNodes[node.ID]
 		nodes = append(nodes, n)
 	}