Added theme switcher

internal/dashboard/templates/layout.html

@@ -14,6 +14,21 @@
 <title>Cloud IP Validator — Admin</title>
 <link rel="stylesheet" href="/static/vendor/fonts.css">
 <link rel="stylesheet" href="/static/dashboard.css">
+<script>
+// Apply a saved theme choice before first paint, so a page load never
+// flashes the OS-default theme before switching to the stored one. Runs
+// synchronously, after the stylesheet link above (browsers block a
+// same-document script on a preceding <link rel="stylesheet"> until it
+// loads), and before body markup starts rendering.
+(function () {
+  try {
+    var saved = localStorage.getItem('theme');
+    if (saved === 'light' || saved === 'dark') {
+      document.documentElement.setAttribute('data-theme', saved);
+    }
+  } catch (e) {}
+})();
+</script>
 <script src="/static/vendor/htmx.min.js"></script>
 <script src="/static/vendor/alpine.min.js" defer></script>
 {{end}}
@@ -60,10 +75,27 @@
 </nav>
 
 <div class="sidebar-foot">
-<span class="pulse-dot"></span>
-control-api
+<span class="sidebar-foot-status"><span class="pulse-dot"></span>control-api</span>
+<button type="button" class="theme-toggle" id="themeToggle" aria-label="Переключить тему" title="Переключить тему">
+<svg class="icon-sun" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><circle cx="12" cy="12" r="4"/><path d="M12 2v2M12 20v2M4.9 4.9l1.4 1.4M17.7 17.7l1.4 1.4M2 12h2M20 12h2M4.9 19.1l1.4-1.4M17.7 6.3l1.4-1.4"/></svg>
+<svg class="icon-moon" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><path d="M21 12.8A9 9 0 1 1 11.2 3 7 7 0 0 0 21 12.8Z"/></svg>
+</button>
 </div>
 </aside>
+<script>
+(function () {
+  var btn = document.getElementById('themeToggle');
+  if (!btn) return;
+  function effectiveTheme() {
+    return getComputedStyle(document.documentElement).colorScheme.indexOf('dark') !== -1 ? 'dark' : 'light';
+  }
+  btn.addEventListener('click', function () {
+    var next = effectiveTheme() === 'dark' ? 'light' : 'dark';
+    document.documentElement.setAttribute('data-theme', next);
+    try { localStorage.setItem('theme', next); } catch (e) {}
+  });
+})();
+</script>
 {{end}}
 
 {{define "topbar_mobile"}}