upd: implement radius setting

to keep things manageable i merged a lot of one off values into just a
handful of common sizes, so some parts of the ui will look different than
upstream even with the "Misskey" rounding mode

packages/frontend/src/components/form/link.vue

@@ -52,7 +52,7 @@ const props = defineProps<{
 	box-sizing: border-box;
 	padding: 10px 14px;
 	background: var(--buttonBg);
-	border-radius: 6px;
+	border-radius: var(--radius-sm);
 	font-size: 0.9em;
 
 	&:hover {