Integrate light theme's `low-sat-blue` using a media query

public/css/icinga/audit.less

@@ -5,7 +5,8 @@
 
   li {
     .rounded-corners(3px);
-    border: 1px solid @low-sat-blue;
+    border: 1px solid;
+    .var(border-color, low-sat-blue);
 
     &.active {
       border-color: @icinga-blue;

public/css/icinga/base.less

@@ -121,6 +121,8 @@
     --link-color: #535353;
     --menu-active-color: #535353;
     --menu-flyout-color: #535353;
+
+    --low-sat-blue: #DEECF1;
   }
 }
 

public/css/icinga/forms.less

@@ -148,7 +148,7 @@ form.icinga-form .control-group .toggle-switch ~ .control-info {
   input[type="time"],
   textarea,
   select {
-    background-color: @low-sat-blue;
+    .var(background-color, low-sat-blue);
   }
 }
 
@@ -338,8 +338,9 @@ form.inline {
   top: 0;
 
   display: inline-block;
-  background:  @low-sat-blue;
-  border: 1px solid @low-sat-blue;
+  .var(background, low-sat-blue);
+  border: 1px solid;
+  .var(border-color, low-sat-blue);
   box-sizing: content-box;
   border-radius: 1em;
   height: 4/3em;
@@ -354,7 +355,8 @@ form.inline {
 
   background: @text-color-inverted;
   border-radius: 1em;
-  border: 1px solid @low-sat-blue;
+  border: 1px solid;
+  .var(border-color, low-sat-blue);
   box-sizing: border-box;
   content: "";
   display: block;

public/css/icinga/main.less

@@ -89,7 +89,7 @@ a:hover > .icon-cancel {
   .action-link();
   .rounded-corners(3px);
 
-  background: @low-sat-blue;
+  .var(background, low-sat-blue);
   display: inline-block;
   padding: 0.25em 0.5em;
 

public/css/themes/icinga-light-theme.less

@@ -5,5 +5,4 @@
 @gray-lighter: #EEEEEE;
 @gray-lightest: #F7F7F7;
 
-@low-sat-blue: #DEECF1;
 @low-sat-blue-dark: #c0cccd;