feat: add missing backend route and frontend utility/config files

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/Frontend/src/lib/socket.js

@@ -0,0 +1,28 @@
+/**
+ * Shared Socket.IO client singleton.
+ *
+ * Import `socket` anywhere in the frontend to use the shared connection.
+ * The socket connects lazily — the first import triggers the connection.
+ */
+import { io } from "socket.io-client";
+// Connect directly to backend to avoid Vite's WS proxy failing on upgrade,
+// which causes an unhandled AggregateError from engine.io's Promise.any() probe.
+// Use the env var when set; otherwise derive the backend URL from the current
+// page's hostname so remote browsers (non-localhost) reach the server correctly.
+const SOCKET_URL = import.meta.env.VITE_API_BASE_URL_BACKEND ||
+    `${window.location.protocol}//${window.location.hostname}:5000`;
+export const socket = io(SOCKET_URL, {
+    withCredentials: true,
+    autoConnect: true,
+    reconnectionAttempts: 5,
+    reconnectionDelay: 2000,
+});
+socket.on("connect", () => {
+    console.log("[socket] connected:", socket.id);
+});
+socket.on("disconnect", () => {
+    console.log("[socket] disconnected");
+});
+socket.on("connect_error", (err) => {
+    console.warn("[socket] connection error:", err.message);
+});