istoreos: write boot done message to process fd/1 instead of /dev/console

/dev/console may invalid on 24.10

```
root@OpenWrt:~# echo hello > /dev/console
ash: write error: I/O error
root@OpenWrt:~#
```

package/istoreos-files/files/etc/init.d/zprintk

@@ -9,8 +9,9 @@ boot() {
 
 	# notify console system is ready
 	sleep 1
-	if pgrep -P 1 askfirst >/dev/null; then
-		echo "iStoreOS is ready!" >/dev/console
-		echo "Please press Enter to activate this console." >/dev/console
+	local pid=`pgrep -P 1 askfirst 2>/dev/null`
+	if [ -n "$pid" ]; then
+		echo "iStoreOS is ready!" >/proc/$pid/fd/1
+		echo "Please press Enter to activate this console." >/proc/$pid/fd/1
 	fi
 }