Yes it's totally possible to put a deck on a webpage and yep you can have it without upscaling!
The trick would be to put the .html version of your Decker project inside of an appropriately sized iframe on the page.
This is how itch.io presents most of the Decker projects uploaded here on the site and as a silly bonus example: here's a tiny deck in an iframe on a plain webpage.
If the iframe matches the size of the deck then it should stay at that (1x) size.
Does this help?