Revert "Move dark mode toggle from sidebar to Settings > Display"

This reverts commit 4ba86429d5.

web/src/layout/AppShell.tsx

@@ -18,8 +18,11 @@ import {
   IconStethoscope,
   IconSettings,
   IconMenu2,
+  IconSun,
+  IconMoon,
 } from "@tabler/icons-react";
 import type { CurrentUser } from "../api/client";
+import { getTheme, setTheme, type Theme } from "../utils/theme";
 
 interface NavItem {
   to: string;
@@ -51,10 +54,17 @@ const roleRank: Record<CurrentUser["role"], number> = { viewer: 0, operator: 1,
 
 export default function AppShell({ user, children }: { user: CurrentUser; children: ReactNode }) {
   const [sidebarOpen, setSidebarOpen] = useState(false);
+  const [theme, setThemeState] = useState<Theme>(() => getTheme());
   const visibleItems = NAV_ITEMS.filter(
     (item) => !item.minRole || roleRank[user.role] >= roleRank[item.minRole],
   );
 
+  function toggleTheme() {
+    const next: Theme = theme === "dark" ? "light" : "dark";
+    setTheme(next);
+    setThemeState(next);
+  }
+
   return (
     <div className="page">
       <aside className="navbar navbar-vertical navbar-expand-lg" data-bs-theme="dark">
@@ -87,6 +97,14 @@ export default function AppShell({ user, children }: { user: CurrentUser; childr
               ))}
             </ul>
             <div className="navbar-footer px-3">
+              <button
+                type="button"
+                className="btn btn-outline-secondary btn-sm w-100 mb-2 d-flex align-items-center justify-content-center gap-2"
+                onClick={toggleTheme}
+              >
+                {theme === "dark" ? <IconSun size={16} /> : <IconMoon size={16} />}
+                {theme === "dark" ? "Light mode" : "Dark mode"}
+              </button>
               <div className="text-secondary small mb-2">
                 Signed in as {user.name ?? user.email ?? user.sub} · {user.role}
               </div>