Presumably with this solution you will need to continually update webclient/login.html after every upgrade of the software.
Alternatively you could (should?) look at doing this via the http server configuration.
I do this on linux using apache, by editing the /etc/httpd/conf/httpd.conf file, example shown below. You will find this at the end of the httpd.conf file:(uncomment out this line)
NameVirtualHost *:80(add this section)
Redirect 301 / https://www.yourservername.com
... then restart the httpd service.
This solution will redirect traffic regardless of the html file being served -- if traffic comes in via http it immediately gets redirected to https.