refactor(prog): move network monitoring outside listener loop

Move the network monitoring goroutine initialization outside the listener
loop to prevent it from being started multiple times. Previously, the
network monitoring was started once per listener during first run, which
was unnecessary and could lead to multiple monitoring instances.

The change ensures network monitoring is started only once per program
execution cycle, improving efficiency and preventing potential resource
waste from duplicate monitoring goroutines.

- Extract network monitoring goroutine from listener loop
- Start network monitoring once per run cycle instead of per listener
- Maintain same functionality while improving resource usage

cmd/cli/prog.go

@@ -530,15 +530,18 @@ func (p *prog) run(reload bool, reloadCh chan struct{}) {
 		go p.watchLinkState(ctx)
 	}
 
+	if !reload {
+		go func() {
+			// Start network monitoring
+			if err := p.monitorNetworkChanges(); err != nil {
+				mainLog.Load().Error().Err(err).Msg("Failed to start network monitoring")
+			}
+		}()
+	}
+
 	for listenerNum := range p.cfg.Listener {
 		p.cfg.Listener[listenerNum].Init()
 		if !reload {
-			go func() {
-				// Start network monitoring
-				if err := p.monitorNetworkChanges(); err != nil {
-					mainLog.Load().Error().Err(err).Msg("Failed to start network monitoring")
-				}
-			}()
 			go func(listenerNum string) {
 				listenerConfig := p.cfg.Listener[listenerNum]
 				upstreamConfig := p.cfg.Upstream[listenerNum]