Add per-browser theme selection

Signed-off-by: DL6ER <dl6er@dl6er.de>

scripts/pi-hole/php/header.php

@@ -168,11 +168,6 @@
     <meta name="msapplication-TileImage" content="img/favicons/mstile-150x150.png">
     <meta name="theme-color" content="#367fa9">
 
-<?php if ($darkmode) { ?>
-    <style>
-        html { background-color: #000; }
-    </style>
-<?php } ?>
     <link rel="stylesheet" href="style/vendor/SourceSansPro/SourceSansPro.css">
     <link rel="stylesheet" href="style/vendor/bootstrap/css/bootstrap.min.css">
     <link rel="stylesheet" href="style/vendor/font-awesome/css/all.min.css">
@@ -187,7 +182,6 @@
 <?php } ?>
     <link rel="stylesheet" href="style/vendor/icheck-material.min.css">
     <link rel="stylesheet" href="style/pi-hole.css">
-    <link rel="stylesheet" href="style/themes/<?php echo $theme; ?>.css">
     <noscript><link rel="stylesheet" href="style/vendor/js-warn.css"></noscript>
 
     <script src="scripts/vendor/jquery.min.js"></script>
@@ -216,7 +210,6 @@ if($auth) {
 ?>
 
 <!-- Send token to JS -->
-<div id="checkbox_theme" hidden><?php echo $checkbox_theme_name; ?><?php if($checkbox_theme_name !== $checkbox_theme_variant){ echo "-$checkbox_theme_variant"; } ?></div>
 <div id="enableTimer" hidden><?php if(file_exists("../custom_disable_timer")){ echo file_get_contents("../custom_disable_timer"); } ?></div>
 <div class="wrapper">
     <header class="main-header">