feat(theme): add theme toggle component and integrate into sidebar

frontend/src/components/app-sidebar.tsx

@@ -20,6 +20,7 @@ import Link from "next/link";
 import { usePathname, useSearchParams } from "next/navigation";
 import * as React from "react";
 import { Avatar, AvatarFallback, AvatarImage } from "@/components/ui/avatar";
+import { ModeToggle } from "@/components/mode-toggle";
 import {
 	Collapsible,
 	CollapsibleContent,
@@ -286,6 +287,14 @@ export function AppSidebar() {
 							</SidebarMenuButton>
 						</SidebarMenuItem>
 					)}
+					<SidebarMenuItem>
+						<div className="flex items-center justify-between px-2 py-2">
+							<span className="text-xs font-medium text-muted-foreground group-data-[collapsible=icon]:hidden">
+								Thème
+							</span>
+							<ModeToggle />
+						</div>
+					</SidebarMenuItem>
 					<SidebarMenuItem>
 						<SidebarMenuButton asChild tooltip="Aide">
 							<Link href="/help">