Small CSS fixup

frontend/src/main.less

@@ -162,13 +162,12 @@ main {
 }
 
 .preview {
-	width: min(95vw, 100rem);
 	/* A4 aspect ratio: √2:1 */
 	aspect-ratio: 1.4142135623730951;
 }
 
-.preview-label {
-	place-self: center;
+.preview-container .preview {
+	width: 100%;
 }
 
 // this is the form layout row container thingy
@@ -220,6 +219,10 @@ main {
 			cursor: pointer;
 		}
 
+		.preview-label {
+			place-self: center;
+		}
+
 		img {
 			width: 10rem;
 			background-color: #fff;