Adjust toast-warning appearance on light theme

tildes/scss/themes/_solarized.scss

@@ -47,6 +47,7 @@ $solarized-base: (
   "stripe-target": $yellow,
   "topic-tag-nsfw": $red,
   "topic-tag-spoiler": $yellow,
+  "warning": $yellow,
 );
 
 $theme-dark: map-merge($solarized-base, (

tildes/scss/themes/_theme_base.scss

@@ -397,7 +397,9 @@
     }
   } @else {
     .toast-warning {
-      background-color: map-get($theme, "warning");
+      background-color: rgba(map-get($theme, "warning"), 0.9);
+      border-color: map-get($theme, "warning");
+      color: map-get($theme, "foreground-extreme");
     }
   }