refactor: update authentication flow to use NextAuth, replace better-auth with axios for API calls, and clean up unused code

utils/axiosInstance.ts

@@ -0,0 +1,13 @@
+import axios from "axios";
+
+axios.defaults.xsrfCookieName = "csrftoken";
+axios.defaults.xsrfHeaderName = "X-CSRFToken";
+
+const axiosInstance = axios.create({
+	baseURL: process.env.NEXT_PUBLIC_API_URL,
+	validateStatus: (status) => {
+		return status < 500; // Resolve only if the status code is less than 500
+	},
+});
+
+export default axiosInstance;