Remove global and classic ArtNet broadcast addresses

Only use per-interface broadcast addresses for auto-detection.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

main.go

@@ -374,18 +374,6 @@ func detectBroadcastAddrs() []*net.UDPAddr {
 	var addrs []*net.UDPAddr
 	seen := make(map[string]bool)
 
-	// Always include standard ArtNet broadcast addresses
-	// 255.255.255.255 - limited broadcast (may not work on all networks)
-	// 2.255.255.255 - classic ArtNet subnet broadcast
-	for _, ip := range []net.IP{
-		net.IPv4(255, 255, 255, 255),
-		net.IPv4(2, 255, 255, 255),
-	} {
-		key := ip.String()
-		seen[key] = true
-		addrs = append(addrs, &net.UDPAddr{IP: ip, Port: artnet.Port})
-	}
-
 	ifaces, err := net.Interfaces()
 	if err != nil {
 		return addrs