Add sACN tab showing universe consumers

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

sacn.go

@@ -0,0 +1,63 @@
+package tendrils
+
+import (
+	"fmt"
+	"sort"
+	"strings"
+
+	"github.com/fvbommel/sortorder"
+)
+
+type SACNNode struct {
+	TypeID    string `json:"typeid"`
+	Node      *Node  `json:"node"`
+	Universes []int  `json:"universes"`
+}
+
+func (t *Tendrils) getSACNNodes() []*SACNNode {
+	t.nodes.mu.Lock()
+	t.nodes.expireMulticastMemberships()
+	t.nodes.mu.Unlock()
+
+	t.nodes.mu.RLock()
+	defer t.nodes.mu.RUnlock()
+
+	nodeUniverses := map[*Node][]int{}
+
+	for _, gm := range t.nodes.multicastGroups {
+		if !strings.HasPrefix(gm.Group.Name, "sacn:") {
+			continue
+		}
+
+		var universe int
+		if _, err := fmt.Sscanf(gm.Group.Name, "sacn:%d", &universe); err != nil {
+			continue
+		}
+
+		for _, membership := range gm.Members {
+			if membership.Node == nil {
+				continue
+			}
+			universes := nodeUniverses[membership.Node]
+			if !containsInt(universes, universe) {
+				nodeUniverses[membership.Node] = append(universes, universe)
+			}
+		}
+	}
+
+	result := make([]*SACNNode, 0, len(nodeUniverses))
+	for node, universes := range nodeUniverses {
+		sort.Ints(universes)
+		result = append(result, &SACNNode{
+			TypeID:    newTypeID("sacnnode"),
+			Node:      node,
+			Universes: universes,
+		})
+	}
+
+	sort.Slice(result, func(i, j int) bool {
+		return sortorder.NaturalLess(result[i].Node.DisplayName(), result[j].Node.DisplayName())
+	})
+
+	return result
+}