improvement: cursor: default if btn:disabled

This is primarily to target the "phone" icon in "call" messages.

I have searched for `<(icon)?button(.|\n){1,400}?disabled`
and there are only 7 matches,
and in those matches, no matter if they're actually affected or not,
I think it makes sense to have `cursor: default`.

Author: WofWca

packages/frontend/scss/_global.scss

@@ -75,6 +75,9 @@ button {
   font-size: inherit;
   user-select: none;
 }
+button:disabled {
+  cursor: default;
+}
 
 a {
   color: var(--globalLinkColor);