Fix form validation flash message color and input borders (#9235)

* Fix form validation flash message color and input borders

* Fix typo

app/javascript/styles/mastodon/forms.scss

@@ -330,9 +330,12 @@ code {
     }
 
     input[type=text],
+    input[type=number],
     input[type=email],
-    input[type=password] {
-      border-bottom-color: $valid-value-color;
+    input[type=password],
+    textarea,
+    select {
+      border-color: lighten($error-red, 12%);
     }
 
     .error {

app/views/shared/_error_messages.html.haml

 - if object.errors.any?
-  .flash-message#error_explanation
+  .flash-message.alert#error_explanation
     %strong= t('generic.validation_errors', count: object.errors.count)