Fix signup layout overflow

src/app/page.module.css

@@ -9,7 +9,7 @@
 
 .shell {
   width: 100%;
-  max-width: min(1040px, calc(100vw - var(--shell-gutter)));
+  max-width: min(920px, calc(100vw - var(--shell-gutter)));
   margin: 0 auto;
   display: grid;
   gap: 28px;
@@ -121,7 +121,7 @@
   display: grid;
   width: 100%;
   max-width: 100%;
-  grid-template-columns: repeat(auto-fit, minmax(min(100%, 460px), 1fr));
+  grid-template-columns: 1fr;
   gap: 20px;
   align-items: start;
 }