feat: accept large JPG and WebP artworks instead of refusing them

Above 150 MB the browser cannot read JPG or WebP in parts, so a large
artwork was refused. It is now measured from its header, graded and priced
with the discount like any other, and placed on the sheet as a full box,
which is exact for JPG. The card says there is no preview and that the team
checks the art before printing.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/site-cart.js

@@ -91,7 +91,7 @@ function carrinho(){
        measurement:x.med?'file':'customer'}
     : {kind:'artwork',width_cm:x.cm,length_cm:+(x.cm*propDe(x)).toFixed(4),
        copies:x.q,rotation_degrees:x.giro||0,mirrored:!!x.esp,
-       measurement:x.src?'file':'customer'});
+       measurement:(x.src||x.semPrevia)?'file':'customer'});
   let layout;
   if(ehFolha()){
     let y=0;