Improve colors with hovering in light and dark mode

Author: pabzm

skins/elastic/styles/dark.less

@@ -257,10 +257,22 @@ html.dark-mode {
 
     .listing li ul,
     .listing tbody td,
-    .listing li {
+    .listing li,
+    .listing li ul li:first-child {
         border-color: @color-dark-list-border;
     }
 
+    #subscription-table {
+        .placeholder {
+            /* color-dark-list-border is a little too dark here, so we use the input border color */
+            border-color: @color-dark-input-border;
+        }
+
+        .hover {
+            background-color: @color-dark-list-droptarget-background;
+        }
+    }
+
     .listing li.selected,
     .listing li.selected > a,
     .listing li.selected > div > a, // this is used e.g. by kolab_addressbook

skins/elastic/styles/widgets/lists.less

@@ -1100,12 +1100,12 @@ html.touch {
     }
 
     .placeholder {
-        border: dashed thin #ccc;
+        border: dashed thin @color-input-border;
         min-height: 1.5rem;
     }
 
     .hover {
-        background-color: lightyellow;
+        background-color: @color-list-droptarget-background;
 
         .placeholder {
             margin-left: 3em;