feat: add Twitter authentication provider and update sign-in callback to include it

src/auth.ts

@@ -1,6 +1,7 @@
 import NextAuth from "next-auth";
 import Google from "next-auth/providers/google";
 import Facebook from "next-auth/providers/facebook";
+import Twitter from "next-auth/providers/twitter";
 import Credentials from "next-auth/providers/credentials";
 
 export const { handlers, signIn, signOut, auth } = NextAuth({
@@ -17,6 +18,12 @@ export const { handlers, signIn, signOut, auth } = NextAuth({
       clientSecret: process.env.FACEBOOK_CLIENT_SECRET!,
     }),
 
+    // Twitter OAuth
+    Twitter({
+      clientId: process.env.TWITTER_CLIENT_ID!,
+      clientSecret: process.env.TWITTER_CLIENT_SECRET!,
+    }),
+
     // Email/Password (Credentials)
     Credentials({
       name: "credentials",
@@ -64,7 +71,7 @@ export const { handlers, signIn, signOut, auth } = NextAuth({
   callbacks: {
     async signIn({ user, account }) {
       // For OAuth providers, sync with backend
-      if (account?.provider === "google" || account?.provider === "facebook") {
+      if (account?.provider === "google" || account?.provider === "facebook" || account?.provider === "twitter") {
         try {
           const res = await fetch(
             `${process.env.NEXT_PUBLIC_API_URL}/auth/social`,