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

lib/auth.ts

@@ -1,44 +0,0 @@
-import { sendOtp } from "@/actions/auth-actions";
-import { betterAuth } from "better-auth";
-import { prismaAdapter } from "better-auth/adapters/prisma";
-import { phoneNumber } from "better-auth/plugins";
-import prisma from "./db";
-
-export const auth = betterAuth({
-	session: {
-		cookieCache: {
-			enabled: true,
-			maxAge: 10 * 60, // Cache duration in seconds
-		},
-	},
-	trustedOrigins: process.env.BETTER_AUTH_TRUSTED_ORIGINS?.split(",") || [
-		"localhost:3000",
-	],
-	user: {
-		additionalFields: {
-			role: {
-				type: "string",
-				required: false,
-				defaultValue: "USER",
-				input: false, // don't allow user to set role
-			},
-			lang: {
-				type: "string",
-				required: false,
-				defaultValue: "en",
-			},
-		},
-	},
-	database: prismaAdapter(prisma, {
-		provider: "postgresql", // or "mysql", "postgresql", ...etc
-	}),
-	plugins: [
-		phoneNumber({
-			sendOTP: async ({ phoneNumber, code }) => {
-				// Implement sending OTP code via SMS
-				console.log("Send OTP in auth.ts", phoneNumber, code);
-				await sendOtp(phoneNumber, code);
-			},
-		}),
-	],
-});