style(toasts): most recent darker than rest

frontend/App.vue

@@ -124,8 +124,15 @@ export default {
 	right: 20px;
 }
 
-.toast:not(:first-of-type) {
-	margin-top: 5px;
+.toast {
+	background-color: $dark-grey !important;
+
+	&:last-of-type {
+		background-color: $dark-grey-2 !important;
+	}
+	&:not(:first-of-type) {
+		margin-top: 5px;
+	}
 }
 
 html {