Fix multi-port device discovery by accumulating universes

Multi-port ArtNet devices (like PD8000) send separate ArtPollReply
packets for each group of 4 ports. Previously we overwrote universes
on each reply; now we accumulate them.

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

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

main.go

@@ -297,8 +297,6 @@ func (a *App) sendOutputs(outputs []remap.Output) {
 
 func init() {
 	log.SetFlags(log.Ltime | log.Lmicroseconds)
-	fmt.Println("artmap - ArtNet Remapping Proxy")
-	fmt.Println()
 }
 
 // parseListenAddr parses listen address formats: