fix: Move CLN sync wait to background to prevent plugin init timeout

- Replace blocking waitForClnSynced with async background monitoring
- Check sync status once during init, continue immediately if not synced
- Start background goroutine to monitor sync completion
- Prevents CLN plugin manager from killing plugin due to 60s init timeout
- Resolves CI test failures where CLN sync takes longer than plugin timeout

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

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

Author: YusukeShimizu

cmd/peerswap-plugin/main.go

@@ -155,14 +155,27 @@ func run(ctx context.Context, lightningPlugin *clightning.ClightningClient) erro
 		return fmt.Errorf("Core-Lightning version %s is incompatible", nodeInfo.Version)
 	}
 
-	// We want to make sure that cln is synced and ready to use before we
-	// continue to start services.
-	log.Infof("Waiting for cln to be synced...")
-	err = waitForClnSynced(lightningPlugin.GetLightningRpc(), 10*time.Second)
+	// Check CLN sync status without blocking init phase
+	log.Infof("Checking cln sync status...")
+	info, err := lightningPlugin.GetLightningRpc().GetInfo()
 	if err != nil {
 		return err
 	}
-	log.Infof("Cln synced, continue...")
+	
+	if info.IsBitcoindSync() && info.IsLightningdSync() {
+		log.Infof("Cln already synced, continue...")
+	} else {
+		log.Infof("Cln not fully synced yet, starting sync monitor in background...")
+		// Start background sync monitoring after init completes
+		go func() {
+			err := waitForClnSynced(lightningPlugin.GetLightningRpc(), 10*time.Second)
+			if err != nil {
+				log.Infof("Background sync wait failed: %s", err.Error())
+			} else {
+				log.Infof("Cln sync completed in background")
+			}
+		}()
+	}
 
 	// liquid
 	var liquidOnChainService *onchain.LiquidOnChain
@@ -519,14 +532,11 @@ func setPanicLogger() (func() error, error) {
 }
 
 // waitForClnSynced waits until cln is synced to the blockchain and the network.
-// This call is blocking with a maximum timeout.
+// This call is blocking and should be used in background goroutines only.
 func waitForClnSynced(cln *glightning.Lightning, tick time.Duration) error {
 	ticker := time.NewTicker(tick)
 	defer ticker.Stop()
 
-	// Add timeout to prevent indefinite blocking during plugin initialization
-	timeout := time.After(45 * time.Second)
-
 	for {
 		select {
 		case <-ticker.C:
@@ -537,10 +547,6 @@ func waitForClnSynced(cln *glightning.Lightning, tick time.Duration) error {
 			if info.IsBitcoindSync() && info.IsLightningdSync() {
 				return nil
 			}
-		case <-timeout:
-			// If not synced within timeout, log warning but don't fail
-			log.Infof("CLN sync timeout reached, continuing with plugin initialization")
-			return nil
 		}
 	}
 }