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>

snmp.go

@@ -246,7 +246,7 @@ func (t *Tendrils) queryInterfaceStats(snmp *gosnmp.GoSNMP, node *Node, ifNames
 		outBytes, hasOutBytes := ifHCOutOctets[ifIndex]
 
 		if hasInPkts && hasOutPkts && hasInBytes && hasOutBytes {
-			key := node.TypeID + ":" + name
+			key := node.ID + ":" + name
 			ifaceTracker.mu.Lock()
 			prev, hasPrev := ifaceTracker.counters[key]
 			if hasPrev {