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

frontend/src/components/mode-toggle.tsx

@@ -0,0 +1,39 @@
+"use client";
+
+import { Moon, Sun } from "lucide-react";
+import { useTheme } from "next-themes";
+import * as React from "react";
+import { Button } from "@/components/ui/button";
+import {
+	DropdownMenu,
+	DropdownMenuContent,
+	DropdownMenuItem,
+	DropdownMenuTrigger,
+} from "@/components/ui/dropdown-menu";
+
+export function ModeToggle() {
+	const { setTheme } = useTheme();
+
+	return (
+		<DropdownMenu>
+			<DropdownMenuTrigger asChild>
+				<Button variant="ghost" size="icon" className="h-9 w-9">
+					<Sun className="h-[1.2rem] w-[1.2rem] rotate-0 scale-100 transition-all dark:-rotate-90 dark:scale-0" />
+					<Moon className="absolute h-[1.2rem] w-[1.2rem] rotate-90 scale-0 transition-all dark:rotate-0 dark:scale-100" />
+					<span className="sr-only">Changer le thème</span>
+				</Button>
+			</DropdownMenuTrigger>
+			<DropdownMenuContent align="end">
+				<DropdownMenuItem onClick={() => setTheme("light")}>
+					Clair
+				</DropdownMenuItem>
+				<DropdownMenuItem onClick={() => setTheme("dark")}>
+					Sombre
+				</DropdownMenuItem>
+				<DropdownMenuItem onClick={() => setTheme("system")}>
+					Système
+				</DropdownMenuItem>
+			</DropdownMenuContent>
+		</DropdownMenu>
+	);
+}