fix(shutdown): force-stop on second SIGINT during countdown

A second Ctrl+C/SIGINT while the 10-second shutdown countdown is
running now exits immediately instead of being silently dropped.
The signal channel is buffered to 2 so the second signal is captured,
and the countdown select exits via os.Exit(1) on receipt.

main.go

@@ -388,9 +388,9 @@ func main() {
 	logger.Info("Finished starting Erupe")
 
 	// Wait for exit or interrupt with ctrl+C.
-	c := make(chan os.Signal, 1)
-	signal.Notify(c, os.Interrupt, syscall.SIGTERM)
-	<-c
+	sig := make(chan os.Signal, 2)
+	signal.Notify(sig, os.Interrupt, syscall.SIGTERM)
+	<-sig
 
 	if !config.DisableSoftCrash {
 		for i := 0; i < 10; i++ {
@@ -399,7 +399,12 @@ func main() {
 				c.BroadcastChatMessage(message)
 			}
 			logger.Info(message)
-			time.Sleep(time.Second)
+			select {
+			case <-sig:
+				logger.Info("Second signal received, forcing shutdown")
+				os.Exit(1)
+			case <-time.After(time.Second):
+			}
 		}
 	}