feat: add unread messages badge and live updates in sidebar

- Display unread message count badge in the sidebar.
- Integrate `useSocket` for real-time updates on unread messages.
- Reset unread message count when navigating to the messages page.
- Increment badge count on receiving `new_message` WebSocket events.

frontend/src/components/app-sidebar.tsx

@@ -45,6 +45,7 @@ import {
 	SidebarGroupLabel,
 	SidebarHeader,
 	SidebarMenu,
+	SidebarMenuBadge,
 	SidebarMenuButton,
 	SidebarMenuItem,
 	SidebarMenuSub,
@@ -54,7 +55,9 @@ import {
 	SidebarTrigger,
 } from "@/components/ui/sidebar";
 import { useAuth } from "@/providers/auth-provider";
+import { useSocket } from "@/providers/socket-provider";
 import { CategoryService } from "@/services/category.service";
+import { MessageService } from "@/services/message.service";
 import type { Category } from "@/types/content";
 
 const mainNav = [
@@ -79,15 +82,46 @@ export function AppSidebar() {
 	const pathname = usePathname();
 	const searchParams = useSearchParams();
 	const { user, logout, isAuthenticated } = useAuth();
+	const { socket } = useSocket();
 	const { resolvedTheme } = useTheme();
 	const [categories, setCategories] = React.useState<Category[]>([]);
 	const [mounted, setMounted] = React.useState(false);
+	const [unreadMessages, setUnreadMessages] = React.useState(0);
 
 	React.useEffect(() => {
 		setMounted(true);
 		CategoryService.getAll().then(setCategories).catch(console.error);
 	}, []);
 
+	// Gérer le compteur de messages non-lus
+	React.useEffect(() => {
+		if (isAuthenticated) {
+			MessageService.getUnreadCount().then(setUnreadMessages).catch(console.error);
+		}
+	}, [isAuthenticated]);
+
+	React.useEffect(() => {
+		if (socket && isAuthenticated) {
+			socket.on("new_message", () => {
+				// Incrémenter si on n'est pas sur la page messages
+				if (pathname !== "/messages") {
+					setUnreadMessages((prev) => prev + 1);
+				}
+			});
+
+			return () => {
+				socket.off("new_message");
+			};
+		}
+	}, [socket, isAuthenticated, pathname]);
+
+	// Remettre à zéro si on arrive sur la page messages
+	React.useEffect(() => {
+		if (pathname === "/messages") {
+			setUnreadMessages(0);
+		}
+	}, [pathname]);
+
 	const logoSrc = React.useMemo(() => {
 		if (!mounted) return "/memegoat-color.svg";
 		return resolvedTheme === "dark"
@@ -193,6 +227,11 @@ export function AppSidebar() {
 										<span>Messages</span>
 									</Link>
 								</SidebarMenuButton>
+								{unreadMessages > 0 && (
+									<SidebarMenuBadge className="bg-red-500 text-white border-none h-5 min-w-5 flex items-center justify-center p-1 text-[10px]">
+										{unreadMessages > 9 ? "9+" : unreadMessages}
+									</SidebarMenuBadge>
+								)}
 							</SidebarMenuItem>
 						)}
 					</SidebarMenu>