feat: add system-aware dark theme

404.html

@@ -6,6 +6,11 @@
   <title>ha.mr - link compressor</title>
   <style>
     @import url('https://fonts.googleapis.com/css2?family=Hammersmith+One&display=swap');
+
+    :root {
+      color-scheme: light dark;
+    }
+
     html, body {
       margin: 0;
       width: 100%;
@@ -78,7 +83,6 @@
       border-radius: 10px;
       margin: 10px 0;
       font-size: 16px;
-      background-color: rgb(230, 230, 230);
     }
     #output-link-container {
       margin: 10px 0 0 0;
@@ -165,4 +169,4 @@
 
   <script type="module" src="/main.js"></script>
 </body>
-</html>
+</html>