Add: Theme switcher

layouts/_partials/body/body-end.html

@@ -1 +1,24 @@
-{{- /* You can dynamically load scripts in this file */ -}}
+<script>
+(function () {
+  var btn = document.getElementById('theme-toggle');
+  if (!btn) return;
+
+  function getTheme() {
+    var stored = localStorage.getItem('theme');
+    if (stored) return stored;
+    return window.matchMedia('(prefers-color-scheme: light)').matches ? 'light' : 'dark';
+  }
+
+  function applyTheme(theme) {
+    document.documentElement.setAttribute('data-theme', theme);
+    localStorage.setItem('theme', theme);
+  }
+
+  applyTheme(getTheme());
+
+  btn.addEventListener('click', function () {
+    var current = document.documentElement.getAttribute('data-theme') || getTheme();
+    applyTheme(current === 'dark' ? 'light' : 'dark');
+  });
+})();
+</script>

layouts/_partials/head.html

@@ -12,4 +12,12 @@
 <!-- Direct custom CSS -->
 <link rel="stylesheet" href="{{ "css/custom.css" | relURL }}">
 
+<!-- Theme switcher: run before paint to avoid flash -->
+<script>
+(function(){
+  var t = localStorage.getItem('theme');
+  if (t) { document.documentElement.setAttribute('data-theme', t); }
+})();
+</script>
+
 {{ partial "head/head-end.html" . }}